Just for clarification, even without going with a proxy workflow, FCP handles most native media formats better than just about any other NLE.
Regarding Resolve, two pointers. The Edit page seems to offer worse playback than the Color page, which makes no sense. Second – edit first, then grade. Do not try to add a lot of grading nodes and then do the editing. Resolve simply gets bogged down in the Edit page, once all of the clips have several nodes applied to them.