Is there (planned) a way to partially regenerate world features? After I updated alien biomes recently, it has tiles now on the new chunks that don't match up with the old chunks, creating a sharp line between them, even though biomes & cliffs match. I don't want to regenerate everything, I only want to make the tiles picture match up.

Also, when I regenerated my map with this mod as it is now, it unspawned all resources. The map received no resources whatsoever except a couple leftovers in the starting area (in active chunks) and some on the outlying borders because I had "/c game.forces.player.chart(game.player.surface, {{x = -2000, y = -2000}, {x = 2000, y = 2000}})" going on, finishing up then.

Resources do respawn unless you have something like RSO installed.

I do have RSO. So it's incompatible? Anyway, is there a way for partial regeneration, as I only want to regenerate tiles? Is it planned?

I don't know that it's incompatible, more like that mod does not handle this case well. The point is that a chunk gets deleted and respawns naturally, any ore that would be there will always respawn, unless a mod stops ore spawning naturally and places it via script. If a mod does that then the mod should do the same thing every time that chunk spawns. If RSO is not doing that then then probably should.

https://mods.factorio.com/mod/rso-mod/discussion/5c9e160b63c10c000b1a57b4
You can mark it as incompatible*.
So how about partial regeneration? :)

*Should run /rso-regenerate separately.