Since if you PB for TPE in Soulless Pacifist it counts (according to the category rules) does that mean you don't have to fully wipe save data before doing a Pacifist run?

It's still mandatory to do before every run, but Soulless Pacifist doesn't require this after Genocide because the 10 minute wait after Genocide, followed by the choice that you make afterwards gives the same results as a full reset anyway, with the only difference being the final ending (Soulless Pacifist Ending).

So yeah you still have to wipe data / fresh reset before every run, but in Soulless Pacifist the 10 minute wait events don't make this necessary.

Okay, that makes sense.

If you want to do Genocide, I recommend using the genocide remover for practice runs https://fucknohtml.tumblr.com/post/133037946850/do-you-own-the-steam-version-of-undertale-do-you

I know how to remove genocide, but thanks.