Missed content:
I think we can start with the edits in the Wizard Editions...
As mentioned, the edits were mostly done to make the book easier/more playable. It pretty much means making the combat opponents weaker.
I've pointed out 4 of the sections where such changes were made.
1) The early Giant Scorpion combat, although the changes was incomplete and resulted in a minor glitch where it lists condition for an Attack Strength level that it can't possibly reach.
2) The Caarth warrior and sorcerer, which unfortunately also contain a similar glitch where the sorcerer is stated to have a different SKILL in another section.
3) The Accursed battle, which is thankfully bug-free.
4) The Snapperfish still have the same stats, although they no longer inflict SKILL penalty. This one, though, isn't a mandatory encounter. We mostly took the optimal path through the book, except for the half-flooded maze portion. It's possible to navigate through this part without any combat encounters.
5) There's 1 other that I forgot to point out earlier: the Great Serpent guarding the sarcophagus actually has a STAMINA of 14, but was reduced to 11. Its SKLL remained unchanged. Reducing STAMINA by 3 points may not seem like much but by shortening the combat it does reduce the chance of it winning 2 consecutive rounds, which would have led to it swallowing the PC whole (Game Over).
There are 3 other encounters where opponents are made weaker. Obviously, the fact that we didn't encounter them means that those aren't mandatory. In fact, one of the encounters is on a path where the book cannot be won at all.
1) That last one I was referring to is in fact Cranno's Sabretoothed Tiger. I
Its SKILL is reduced from 11 to 9 (STAMINA is 8). The original SKILL actually fits the one listed in Out of the Pit. This change is really kind of pointless, since you only have to fight it if you attack Cranno, and if you attacked Cranno, you essentially can't win the book, since you can't trade any items with him and therefore can't get the necessary Papyrus Scroll. So while the change makes this fight easier, it doesn't make the book easier. You fail either way.
The other 2 encounters, while not mandatory, are at least not on a sure-to-fail path (I think...not sure about the first one).
2) There's a Death Spider (Spider-headed demon) encounter, with SKILL 14 STAMINA 9 in the original version. Again, this actually matches the Out of the Pit stats, but in the Wizard edition, the SKILL is reduced to 12.
3) We chose not to investigate a treasury. If we'd gone in, we'd encounter Akharis' undead Vizier, Amentut. The changes to this combat is slightly more complex. He's been made weaker in terms of stat (SK 9 ST 8 to SK 7 ST 7). He also has the power to drain your stats if he hits you. The chances of that happening is actually INCREASED in the new version (1/3 instead of 1/6), and he drains 1 SKILL and 2 STAMINA off you (and gains the STAMINA himself) instead of 1 SKILL 1 STAMINA in the old version. Note that the drain is to
both Initial and current stats. So this opponent is both easier and harder in different ways that it's hard to judge either way.
As mentioned, it's not necessary to face him at all. The treasury is genuine, but gold is completely useless once we're past the initial stage of the book. We also find a Bronze Rattle in the room, which is one of the items that will be checked it we choose to use "other charms" against Akharis (and does nothing at all besides letting Akharis get a free hit on you).
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Regarding the liquids in the embalming chamber, the sweet-smelling liquid restores 4 STAMINA and also gives you a temporary give you +1 Attack Strength for one combat. However, that Attack Strength bonus will be used up almost immediately, since once you try any of the liquids, you won't be able to leave the place unhaindered, and will go through an unavoidable combat encounter (more on that later).
The foul syrup will poison you if you try to drink it, but it does toughen your skin if you rub it on yourself. But this too is a double-edged sword - it reduces all external STAMINA damage done to you by 1 point (including combat), but it also gives you a permanent -2 SKILL penalty (makes you less flexible),
As mentioned before, there will be a combat encounter once we try any of the liquids, so it might well have been better for us not to try any. We would have encounter 3 animal mummies: tiger, jackal and snake.
Even mummified, the snake's bite in poisonous. Also, like all another mummy encounters (not counting Akharis), each can be destroyed with a fire source, or you can do double damage by fighting with a torch.
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Regarding other items we picked up/could have picked up in the game (I'm not listing the ones with obvious functions like healing draughts and anti-poison):
The Alabaster Scarab acts as a lucky charm that gives you a 1-point bonus for every Luck test, so it's actually pretty useful, if we'd had the money to spare for it.
Yokka Eggs work almost exactly like Firepowder most of the time (which is why it's puzzling that the latter isn't listed as a possibly fire attack source most of the time). The Firepowder as we know has the additional function of being used like explosive to blow up objects outside combat, like Akharis's sarcophagus, or alternatively the rubble blocking a door. Yokka Eggs, however, can be used to keep us warm at one point when we were sleeping outdoors, protecting us from cold without having to light a fire and attract possible enemies.
The Sandworm's Tooth is actually made into an ivory dagger commonly used by the desert nomads, but the PC doesn't get any benefit from it, since it's not a familiar weapon. It was checked during the Sand Golem encounter, but gives us no advantage and instead brings a SKILL penalty. Fire and the statuette of the god were the only 2 things that work on the golem.
The carved bone horn is actually checked when we encounter some Xoroa Warrior in the desert:
However, it's a trap option - blowing the horn only draws more of the creatures. They carry similar horns themselves to summon each other.
The Sealed Black Bottle is another pure trap item. This one is lethal if you ever open it - it contains a Nanka that sucks you into the bottle forever.
The Book of the Dead gave us essential information to pass the Sphinx, but it's also used as a trap option against Akharis. He throws us around while we're busy looking through it for a spell.
The Iron Wand is the worst item to use - it boosts Akharis's SKILL by 1 point and STAMINA by 3 points.
(So yes, choosing to use "charms" against Akharis just gives us a list of useless/detrimental options. Speaking of which, using fire doesn't work either. This one actually kind of makes sense, since we were able to deal with almost all the other mummies with fire, so it makes sense that the Cult will take extra precautions to set magical protection against the obvious weakness.)
Successfully removing Akharis' mask will take 1 SKILL and 2 STAMINA off him, but it's not really worth the effort - you basically need to fight him with a -3 Attack Strength penalty, and only succeed if you score an Attack Strength that's 3 point higher than his (so essentially equivalent to a 6-point penalty!). If your SKILL is high enough for that, you're probably better off just fighting him normally!
The Waters of Life, when drunk, restores half your Initial STAMINA, 2 SKILL, 2 LUCK and reduces POISON score by half as well.
Rolling the best possible result at the restorative pillar will give you full restores in every stat, remove all POISON, and give you a +1 Attack Strength for the rest of the book.