Just took the plunge to buy Resolve after completing a test project. We are Vegas users and our workflow uses VMIX to record multi-cam sessions using MJPEG codec. We need a more cross platform solution for upcoming multi-editor event.
This workflow has been working for us for the past year, I don't feel the need to increase our disc usage.'
We run 1080 at 25p and final product has been fine for a couple of years
In this project, one camera was 4k, the rest 1080.
The switched output is AVI Declink MJPEG format and the Multi-cams are AVI MJPEG DMO (as one is 4K input) - source footage looks fine, no aliasing.
But in the preview it looks less quality and most noticeable in the render

I have rendered out multiple test sections at different codes up including hi data rate AVI etc, our usual delivery is H264 mp4 for Youtube at around 20mbs with 512kpbs audio (our content is audio focussed).

The rendered video output is not good, we are used to not seeing aliased jaggy edges but in all tests, we do via the resolve workflow, but not via the Vegas edit route.
It looks like badly upscaled 720, but the source is 25p 1080 and 4k

Any suggestions as to why this might be happening?

Windows 10 machine 32GB RAM, NVIDIA 1060 6GB CUDA, VMIX resolve 16.2.5
All works fine Vegas.