I think this Gears strat is fastest:

Go to the left first, grab Double Jump. Start combo from other side, only finisher has to hit the gears. Grab Air Slide gear, turn around and get gear in the pit. On the way up, Double Jump and Air Slide to get to the next Gear, faster than walking.

For bosses:

You can use magic and get multiple magic finishers at once, potentially, you can get Thunder, Fire and Blizzard finishers and do a ton of damage at once to bosses.

You can also skip Blizzard during the Aqua Clones. She laughs right before she appears, you can use Thunder to stagger and interupt this cast, saves a ton of time if you get bad RNG. Shout outs to Barbaracle to noticing that one.

Wanting to get into the Ape Escape speedrun because it was one of my favorite games as a kid, plus the infinite jumps and movement just looks awesome.

I've watched Markhest1's tutorials and eednob's level guides, but is there anything else? I've been trying to learn from SSBMstuff's WR video but he's a monster and his play is ridiculous looking.

Lastly, does the model of PS2 and region of the game matter? I've seen some games specify what kind of PS2 it is (slim, super slim, fat) when submitting runs, but I don't see it here.

Since you can't play JP on a US GameCube, is text the only time saver, and is it known how much time it saves?