My preferred way is ffplay(1). Last time I checked I get lower latencies than OBS at that, at least when I use `-sws_flags fast_bilinear`, which is the same scaling OBS uses by default.
I wouldn't wish bilinear scaling on my worst enemy; 1:N is the only way to go for me. I'll check out ffplay.
Edit: ffplay doesn't support cropping the output to fit my display (or if it does, it's far too arcane for me). As composable as ffmpeg is, it's awful UX for me. I'll stick to OBS.
Use whatever gets the job done. As for scaling and cropping, to the best of my knowledge, ffplay(1) supports all the options that ffmpeg(1) does. Here is what I for example use when capturing my Famicom: ffplay -sws_flags fast_bilinear -framerate 60 -video_size 1920x1080 -vf crop=iw-360:ih,scale=-1:1080 $DEV.
Edit: ffplay doesn't support cropping the output to fit my display (or if it does, it's far too arcane for me). As composable as ffmpeg is, it's awful UX for me. I'll stick to OBS.