I always edit it in its purest form - Whatever size and format is was recorded in, (4K 60FPS) then export a full quality version. Then, with my editing program still open, I export various versions of same video - 1080p, 720p or whatever format I need .mov / .mp4 / .mpg / .avi (etc)
I edit with Davinci Resolve - Professional Quality - &... Completely Free
https://www.blackmagicdesign.com/pro...davinciresolve