There isn't a way to set the BPM of the video, directly. You can, however, create a Media Sequence with MixEmergency's Media Sequence Editor. This would allow you to set and save a BPM for the video within that sequence (you can have a sequence with only one video). As for what is better to play back in MixEmergency - generally I would say the MP4 file. The codecs that work best in MixEmergency are things like H.264, H.265 (if you're using macOS 10.15 or higher), and Hap (for short samples and loops). All of these formats can have their video decoding accelerated by the graphics processor, freeing up your CPU.
