When going into the mirror that takes you to the room with the pillars, you can do a thunder on the stairs to hit some of jars around the mirror to get some extra hits in. Also, hits from the Aqua 2 fight carry over after the fight so that helps with building up the arrows as well. You can also get 3 hits in on Aqua 3 at the very start of the fight where she transforms into spellweaver. Hope that helps!
DM Skip for Final Xehanort. I was able to get this relatively consistently in practice, not sure if things would line up exactly in a run though. Didn't eat the food in this video either. Depending on your level/Ever After level/if you ate the food, you can just go lower or higher on the first shotlock and it should be fine. Just don't want to hit the DM HP gate before doing the fifth fire in the last combo to be safe since he does have a chance to get out after the 4th one and DM if you're too far away for the fires to consistently stagger him.
I'm 100% in support of a split. It can be extremely discouraging for anyone who wants to learn the run, but then sees that they'll never be able to get close to WR, or they'll always be behind just because of the hardware that they're on.
In addition to that, with the shotlock and framerate differences the runs do play out pretty differently depending on the system you're on. If someone was trying to learn the run and went to watch a video of WR, they'd see strats like the Darkside 1 and 2 fights that simply wouldn't work on a base PS4. Aqua 3 and Forest Fight are way more consistent on PS4 Pro due to the higher framerate. Demon Tide is also just a slower fight in general on base PS4 because of the shotlock differences as well. There's a lot of differences here, so I really think a leaderboard split would make sense.