I've been very interested in running this, but I don't have a capture card. What are the guidelines for using a emulator?

just be legit with it, no save stating, speedup, ya know, invalid things. Also, putting on the fps cap at 60 helps to make sure you arent going over accidentally(yes i realize sometimes it fluctuates between 59 and 61, thats fine). other than that, if you wanna run 8x res and make it beautiful and better looking than p5, thats on your cpu to be able to handle it.

Can I use a Mobile PPSSPP emulator?

It's the same emulator on a different platform so I guess it's allowed. Same rules obviously still apply, so no closing the game during the run, no emulator's reset function, no save states, no speed ups etc.