I'd definitely join right away, since there's still quite a bit of viability with demo speedrunning.

By NA being excluded, I guess ai_telivion means that there is no NA demo (probably due to that March 4th rumor thing, which might be true considering the other regions). You can still download the EU or JP demo on an NA Switch, which is what I did personally.

Fire seems to slightly farther in terms of distance although that may be because of the jump

EDIT:

Just tested, fire and cutter have the same distance. Not sure which is faster but both seem perfectly viable.

In addition to IL, maybe a full demo% category for both levels?

From what I can gather, these levels seem to pull rooms from other levels throughout the final game, but there's nothing stopping us from just adding "Grasslands" and "Cave and Castle" as IL runs or something like that

In air, fire seems to be faster whereas cutter is faster on the ground (due to a longer distance + similar cooldown time to fire)