Trying to apply and understand downstream source clip effects

Intent: preserve full pixel resolution of 5.8k, 4:3 source clip for maximum reframing flexibility downstream in QHD or UHD.

Project: three camera angles in a multicam sync sequence, and a derivative multicam edit sequence.

How do I apply source clip effects, specifically scale, that can be changed downstream on the edit timeline? For example, if I wish to at least fill a 16:9 frame with an otherwise 4:3 source as a starting point.

I THINK I understand the differences between fit to frame (doesn’t rasterize) and scale to frame (rasterizes), and have been using Fit. Seems like Fill Frame should be a flexible option too.

I have been setting up these sequences as QHD; but perhaps the sync sequence should be same as source? As it is now, I lose maximum reframing flexibility on the derivative edit sequence (I can no longer “zoom out” and I don't know why.

Thank you!!

I’m working in 26.2.2 (non beta)