Davinci is truly great for editing and general post stuff. The Fusion page can certainly composite, but one thing I'm learning with all these various software mainstays and their alternatives - the ones you subscribe to, the ones you can buy, the ones that are free - is that you get whatever the respective feature set is, but you also then get, or don't get, whatever the tutorial ecosystem is that accompanies it. So, just on design and artwork, Adobe means you have to subscribe to the Cloud to get whichever software from them that you're after, but you also get thousands of tutorials and hundreds of good to excellent tutorial channels and courses with it. And for my purposes I'm starting to now see that as being nearly as important as what the software can do.
Fusion can composite and there are a handful of courses or videos out there showing a few things, but you'lll then see long Reddit pages with various posters unhappy that it can't do whatever Nuke or (in some instances) AE can do, or you'll have some guidance from one guy on one channel, but not much more. Whereas if you say 'okay, I'll composite in AE' the big problem will be to decide which of the many tutorial guides to watch first. I've actually moved towards doubling-back and learning / relearning all the Adobe stuff I never really 100% knew, which will keep me busy for a while.
This is a longwinded way of saying I recommend you do a rough mucking-around render-to-Davinci post experiment first, and see whether you end up going 'yeah, this looks fine', or whether the process makes you slap your forehead and pick AE instead. Here's a guy below doing some stuff in C4D with Arnold and then sending it to Fusion.