I'm thinking about speedrunning this and I just wanted to ask if playing as a guest character ONLY on swordplay is fine, I have level 25000 on swordplay so I think the CPU I'm fighting against will be a tad bit harder than a noob beating the first boss (Ryan).

Just use a different Mii

Yeah, the guest save file is deleted after you go back to the Wii menu or turn off your console