Advice for MM4? Or rather for World of Xeen since the GoG version only offers that. From what I understand the 4 and 5 are very connected and then a unique version came out right? Is the druid useful in MM4? In MM3 I used it and in the end I would have preferred to find a Ranger who could at least use the bow!
Sorry a little late to the party, I hope this is still useful advice. Yes, MM4 was initially released standalone, with multiple things that just did nothing (the reflectors, the pyramids, one of the Sphinxes, 2 of the towers, 1 of the dungeon, maybe more I don't remember). Then MM5 came out, you could either install it standalone and play it on its own, or it installed on top of MM4 and formed World of Xeen, with the ability to go back and forth between the worlds, the full campaigns from both, and then an extra bit after you completed both main games. Then WOX was released on its own, the same version as you'd get by combining the games came on some compilation, and then there was the WOX CD version which came on 2 CDs. All versions of WOX, no matter how you get them, are identical in gameplay IIRC.
Druid/ranger in MM3 have their own spellbook with unique spells, and only little overlap with the sorcerer or cleric ones. In WOX they instead overlap with portions of both other spellbooks and no longer get anything unique, but the spells they get are also the more basic and frankly least useful ones, I never considered a druid/ranger a replacement for either a sorcerer/archer or cleric/paladin in WOX. The starting party has a ranger, and it's often the only one I replace (often with an archer).
I don't remember the specifics of the puzzles you mentioned in MM3, but I think every puzzle can be figured out by hints alone (some are tougher than others). The mirror words you find in the pyramid are probably just to make endgame travelling speedier and less annoying, I don't think you can get them earlier.