Animate output problems AGAIN!

This is REALLY winding me up now! ANOTHER output problem. I am creating two files with identical content. One is 1080x1920 HD, the other is 1680x675. All items on the artwork are repurposed to suit the size and shape and the main items are vector-based. When I export to Video/Media to create a .mov file (Quicktime/Default (Animate)), the 1080p screen vectors are nice and sharp. Using the same settings to export the other file, it's blurred. I've tried EVERYTHING to get the settings for the landscape version to work and it just doesn't make sense that it works for one and not the other. I have tried this on both Intel and M2 Macs but no difference. I have SOME hair left, but not much!