BMD has published an excellent series of introductory video tutorials and 5 training books (available for free in PDF form, along with media and project files to follow along). Going beyond just showing how to do X, I think they do a great job of communicating best practices, workflows, and things like keyboard shortcuts that might be useful. This is some of the best educational material for any such application that I have come across (paid or free), and I enthusiastically recommend checking it out.

https://www.blackmagicdesign.com/products/davinciresolve/tra...

I agree that there are less Davinci Resolve tutorials than for Premiere Pro, probably because of the current marketshare. But at least in my bubble, the marketshare of Premiere in shrinking fast, in favour of Resolve. I'm myself not super concerned about having less tool-specific tutorials as I'm on the level where specific tools matter less, and I'm more focusing on the overall pictures (similar to software development where once you have many languages under your belt, many of the more similar ones blend together).

Regarding plugins, last time I checked, Premiere still doesn't support OpenFX (but might have changed). It's just a matter of time before the ecosystem for OpenFX is way bigger than anything Adobe could ever dream up.