Issue creating a Multicam Clip from mixed format source clips

The interviews for the project I am working on were delivered as 6k BRAW files (6144x3456), and Canon avI0 files (2048x1080). Timecodes do not match. If I select the corresponding clips in the Media Browser and use the audio to synchronize, I end up with one camera angle displayed correctly, while the other is zoomed in or shrunk down in the frame. I actually want the mulit-cam to be accessing the proxies (which are all 1920x1080), but I'm not seeing an option to do that. I'm working in a Production, if that makes a difference. 

With Gemini AI's guidance, I've tried at least a dozen ways to create a multi-cam clip from building sync sequences. I wish I could relay all the different things we tried, but it gives me a headache just thinking about it. It always ends up as a multi-cam sequence with all audio channels mixed down to one channel, never a multi-cam clip with discrete audio channels in the bin that I can then open in the source window. I'm at my wit's end here. Someone explain to me the correct way to do this, and keep in mind that I am new to Premiere and am used to having a team of AE's to take care of this on my normal television jobs, so this is all new territory for me. Be gentle and explain it to me like I'm a five-year-old. Thank you!