Most efficient way of queueing video in real time (jit.world/vizzie)

Forgive me for my ignorance, but I'm in the process of building a crude video sequencer(?)/mixer that basically selects midi notes from Ableton Live and bangs messages into a jit.movie~ and uses control vinyl to control the rate of the video. I am also using 4 jit.qt.movie objects which take RT signals from Live and select random video files and overlay them. I am mixing all of the video using vizzie mixers. The set up works, but is not always reliable - sometimes the audio from Max will have a noticeable delay, or sometimes my jit.world will crash entirely but the patch will still be running and I cannot get the jit.world back without reloading the patch. It also seems that the longer I have it open the less reliable it will be. As a beginner - I feel I am probably making mistakes somewhere, or my computer simply doesn't have enough juice to run a Live set with all this video playing in Max.
So my questions are:
What is the best codec to use with Jitter? So far I've been using Apple Prores LT as I have found it to be the least intensive but I could be totally wrong. It seems my computer has a harder time loading the smaller H.xxx mp4 codecs.

I am using 640x480 video at 25fps, but have the jit.world set to 240p - I do not need resolution, as timing and reliability are more important. - Should I just be using all QVGA source clips?

Rather than banging messages to load video clips, should I just be using one big video file and jump around from frame to frame?

My set up is a macbook air m1, and im using mostly vizzie objects for mixing/effects.

I can share the patch if needed but hopefully I explained it okay here.

thanks!