Final Cut is very different to Avid in regards to its timeline. In Avid you have your project setup/framerate from the beginning and the timeline always reflects that. In Final Cut you can have all sorts of different standards in multiple timelines. So, whatever format/codec you have made your source footage, also use those same settings for your timeline. You won’t need to render if you do that.
As for using Avid Codec source files in Final Cut… never had an enjoyable working experience with an Avid codec based timeline. It’s very possible it was something I was doing that affected it but nevertheless, use another FCP friendly codec if you can.