So you want to use deko3d for maximum speed and minimum bloat?
Great!
deko3d is fantastic, working on the same layer of abstraction or even lower than Vulkan, but (even without the C++ wrapper) you tend to only need half as much code to do the same thing.
I've used it for a while now and kind of done the same thing wrong one too many times, so here's a list of those things.
Some things listed here are also documented in the primer while others are not documented there.