You can toggle everything except the texture pack right now, unfortunately. The live reloading is super rad, I've had a blast toggling bloom on and off and laughing at how generic the game looks without it.

I think textures are a fairly new feature, you currently just throw them in an unmentioned folder and it works. But I've heard one of the devs is apparently looking into modding support, so hopefully texture packs can be distributed via mods, and easily enabled/disabled there, similar to Majora's Mask Recomp.

Yes you can. Mid-game without having to restart