the easiest way to to make them look pretty is first AE glow/trapcode shine effects on your computer , then use color finesse soft clip smart limiter to gradually make them legal signals.
yes, if you have CS4, and a size that isn’t a preset to match exactly, then the stretch trick inside AE won’t work. You’d have to use the Adobe media encoder and import a AEP comp file from it, ususally your final comp.
well i think for shots where the lighting/saturation changes, you have to use clone tool with ALT key. That copies the lighting/saturation changes 10 pixels over. and blur/noise/grain is your friend.
try setting memory to default or even a little lower than that. that way the memory won’t crash the render. and a tiff sequence would save time from where it crashed before.