There's a guide here: https://www.speedrun.com/adofai/guides/918k7

Strict timing only shows up as an option for fast songs, you'll see it a lot when you download customs. For the base game, XT-X is the only song that has strict timing. (The rest of the slower base game songs use the same formula as Strict Timing, from what I've heard.)

So no, perfects only does not need to be on and strict timing only applies (right now) to XT-X.

Here's a run I did of All Worlds Any Speed %, hopefully that gets the ball rolling.

Also might as well add on to this topic, EMOMOMO's world designation was changed from ME-X to MO-X, would it be possible for the level category's title be changed to reflect that?

I agree. I'd really like to try an Any Speed% variant that involves all official levels. Right now, the avenue available to us for that is 100%, but that also involves playing a lot of songs twice for all lanterns.

Now that the Muse Dash collab levels are out of Beta, will they be required for the 100% runs?

Also, speaking of 100% runs, is a wiped savefile required for the category? I noticed the current top run starts with Options and OFN at the beginning, and I'd much rather start with those than leave them for last.

Just wondering, what about it makes it "too messy"?

It's probably my favorite category because you can just go without pausing to think, would definitely love to submit runs if the category existed.

So a few days ago, JPrez became the first person to do a guitar FGFC speedrun of RB2, with a final time of 9:31:15 - for anyone who didn't already know: