I don’t recommend editing with AMA linked media other than under very specific conditions. I suggest AMA link and transcode which creates Avid native media a lot faster than an import as the transcode processes uses all cores versus the one of an import. But if for a couple files, then it may end up being a wash.
When changing the playback rate in source settings, it is doing a frame for frame playback to the project rate. So in your example, 23.976 would play back faster at 29.97 (20% faster). Audio also gets adjusted and sample rate converted to stay in sync, but pitch is not corrected.
Michael