RTF is a global modification that replaces all towns in the game.

1) and 2) SRD worked on the skill wheel; the decision was made to revert to the old schools of magic and rework the main skill upgrade, replacing some with more logical ones. I don't remember the details, as it was a while ago.
3) The plan was to add neutral creatures.

Yeah, that's right :D - sorry for the expectations - I needed a break from Heroes, and I got hooked on Total War: Warhammer (mainly Mortal Empires). I learned a lot of new things there and, in part, re-evaluated my view of strategy games (many of the things I don't like in Heroes are presented differently there, or don't exist at all). I definitely want to return to Heroes.
P.S.: We decided not to leave the old schools as they were, but to move the wheel from Harmony to RTF (with adjustments to racial perks), meaning the original magic will be included.