If I plan to shoot some footage in 720p60 for the sake of slowing down in post, should I go ahead and shoot the rest of my footage in 720p to match, or does it make sense to shoot the rest in 1080? If I do the latter, should I import the clips to a 720 or 1080 timeline?

Also, I understand that conforming 60p to 24p gives good natural 50% slow motion, but what if I want my final footage to only be 20% slower than my original footage? For example, if I shoot a music video at 125% speed and then slow it to 80% to get that cool dreamy look would I still want to film in 720p60 or would 1080p24 work as well?