Nicely done, I can’t see the join. Is that AviSynth’s AutoOverlay?
Yes, it is. Use it too?
I tinkered with it for one shot of my Freddie Mercury video, but couldn’t get it looking as good as you’ve done so ended up just aligning it manually in Resolve. My two source videos were rather different from each other in exposure, colouring, noise/grain, etc…