HDV is the WRONG choice.
Convert the GoPro footage to ProRes 422...the same frame size you shot (720 or 1080). Use Compressor or MPEG STREAMCLIP. Then import into FCP. DO NOT edit the native files that come from that camera. FCP will hate you.
People generally shoot 1080p, unless they want some footage to be used as slow motion, in which case they shoot 720p60, and slow that down (conform with Cinema Tools) to 30fps or 24fps...to match the project.
ProRes 422 is fine. The other, HQ, is too big for this format. Larger file sizes with zero benefit.
DO NOT SCALE! Scaling in MPEG STREAMCLIP is bad. If you want 1080p...shoot 1080p. If you shoot 720p to get the slow Motion...upscale with COMPRESSOR. It has a better scaling engine, if you go into the Frame Controls and turn everything to BEST. And wait...wait...wait...as it does this. But shoot what you want to post. That's how you get the quality you want.
Oh, and light well. The GoPro isn't good in low light. Not at all.