More info from a community meet-and-greet/Q&A session Star.Theory held at PAX:
https://twitter.com/badnewsbaron/status/1166829617514041344?s=19 (clickthrough for thread)
Related Reddit post: https://www.reddit.com/r/KerbalSpaceProgram/comments/cwrj0e/a_friend_of_mine_got_out_of_a_meeting_with_star/
reaffirmed no microtransactions--sticking to KSP 1 release style
Trailer made with in-game assets
Kerbin is geographically the same (albeit prettier). Other planets got facelifts. Same planets in the system. Engine now supports axial tilt.
"No two landing sites should feel the same". Also better lighting and shadows (even from moonlight).
New systems: multiple, exact number not specified.
Better craft building--improved subassembly system, blueprint mode for easier placing and alignment, larger VAB.
Physics/orbital mechanics/etc. not dumbed down, it's still KSP. Better tutorials tho, at least some fully animated.
Build colonies anywhere. Expansion directly player-driven only. Meant to be springboards for exploration deeper into space.
PC optimization comes first, but S.T are well aware of the problems KSP1 has had on consoles and fully intend to do right by the console community.
Much higher part counts, but no specific numbers yet.
Kerbals subject to G-forces. Affect animations; they can even black out. Also more animated in general. Also have emotes.
Planetary rings include large rocks
Explosions different for different situations (atmo/vac, fuel/empty, etc.). "Every explosion should be a special snowflake."