Ghul wrote:

someone trying to cut themselves out of the belly of a giant toad

These have been the most memorable times Weapon Class has come up :D

Do I understand it correctly that first the winners of initiative do melee, then the losers, then the winners shoot missiles, then the losers, and so forth?

I am mostly curious about the changes to the monk (because one of my players loves the idea but wasn't that satisfied with the execution; still, he played a monk at least once in all our campaigns) and the combat system.

Party composition is the first tactical choice, and one whose import shouldn't be underestimated

(Of course, there's nothing wrong with everyone just rolling up random characters or everyone playing the class they prefer, but the game certainly rewards certain compositions through increased survival rate.)

Wow, these are great! I especially love the idea of having a picture showing the location from the outside.

I have a hard time figuring out how the Tower's levels are connected, though :/

I'm terribly sorry to hear it

Think of it as having four steps:
1. winners of initiative perform their Phase 1 actions
2. losers of initiative perform their Phase 1 actions
3. winners of initiative perform their Phase 2 actions
4. losers of initiative perform their Phase 2 actions

I've run Barrowmaze, Rappan Athuk, and Dwimmermount. Each has their strengths and weaknesses (Barrowmaze has the slickest room descriptions at the cost of sameness; Rappan Athuk is the most wild, but the text is meandering and the editing is bad; Dwimmermount has the most internal consistency, but there's a lot of info that needs to be internalised to make use of that). I've written about my experience about them here: https://ynasmidgard.blogspot.com/2018/06/lessons-learnt-running-megadungeons.html

Based on reading alone, I find Anomalous Subsurface Environment and Castle Xyntillan the most fun (the latter also showcases a great style of presentation). The Darkness Beneath (the serialised megadungeon of Fight On!) is also a pretty good read, but also naturally varying in quality. The upcoming Arden Vul might be the best published megadungeon ever based on the preview material (periodically posted on MeWe) - but the proof of the pudding and all that.

I found the Tome of Adventure Design from Frog God Games to be the single most valuable supplement to any kind of D&D-esque game.

Since Identify can only follow a successful Appraise, it's worth noting that the chances of actually identifying magical properties is lower than the X-in-12 first indicates (with 16+ INT chances in parentheses):
Lvl 1-2 - 10.42% (16.67%)
Lvl 3-4 - 16.67% (24.31%)
Lvl 5-6 - 24.31% (33.33%)
Lvl 7-8 - 33.33% (43.75%)
Lvl 9-10 - 43.75% (55.56%)
Lvl 11-12 - 55.56% (68.75%)