basically you want to make a new sequence, the size of your native resolution then, attach it to an adjustment layer – adjustment layer the size of the new desired resolution. Then render a precomp. After you render the precomp lossless animation, open a new sequence with the size you want to finish at. Import the precomp. and go to filters > scale> and scale it up till the adjustment layer is gone and all you see is your footage filling the window.
Go a row or two pixels larger than you need. Then render it out as a cropped image. Then reimport the cropped image and duplicate it, on the duplicated layer=behind main image add smart blur and this should help seal any pixelation. Also boost up the color a bit on the layer with all the effects on it. maybe set the top layer to 98% opacity . Render it out as an animation and bring it into the cutting board. Happy cutting.
This is what I would try.
so, layer with effects goes behind the layer without effects.
Layer with no effects is at 98% opacity, layer with effects is at 100, boost up the color on the layer in without the opacity.
“Oop, I think my render is done!”