Even this week I still had the issue where I couldn’t decrypt messages in Element on android.

Not gameplay but phone camera footage, but I always convert to h264 using a CRF of 18. CRF is like a quality factor that adjusts bitrate based on how much movement there is. Lower CRF means more quality. More modern codecs like h265 and AV1 can produce even smaller files than h264, but ofc it’s best to just do lots of tests.