Title. I want to get a JP copy to run this game.
Also, why is wr not on WiiUVC? Looking at the glitch/trick list it seems like there's a lot of Wii U exclusive timesavers.

1: Ebay, Amazon, etc. You can find Japanese copies for really cheap to import.
2: Far as any of us are aware VC offers no exclusive glitches. WiiUVC for North America runs on version 1.1 of the game, while most NA cartridges run on 1.0 which has some glitches that only work on that version, meaning WiiUVC actually has fewer. (Also glitches that crash on DS dont seem to work on VC either if what the rest of the community has told me is true). The North American version is significantly different from the European, Japanese, and Australian versions, which is where the actual differences come from. Although the NA version has exclusive glitches, it also has a final boss with 9500 HP across 3 phases, while all other regions it is 5500 across the 3 forms.

Considering EPS is an utter nightmare in any% and nearly all the big region-specific happen after Gritzy Desert, the NA version is inferior for any%. All bosses has a similar problem where every boss has significantly higher HP values, mitigating potential time save. Also many glitches have only been found to work on emulator and crash on console.

The WR is not on WiiUVC in part because the top 3 runners of the game (Snoion, Anwonu and myself) are all from the Americas (meaning we dont natively have access to the WiiUVC of Japan or Europe). While VC injects are a thing, none of us have really bothered, although I personally dont know if it would really save much time if at all. (Also WiiU has lag which sucks for trying to do frame perfect inputs and Copy Flowers, but thats more preference).

The trick list lists many glitches as "U-Only." If it isn't talking about Wii U is it talking about USA cartridges?

Yes it is talking about the USA cartridges. The Wii U VC version of the game patched all the glitches that are listed as "U Only" while also keeping the increased boss health. Therefore the NA Wii U version is the slowest version to play on.