It's a drop-in replacement for the nvidia package. AFAIK there are zero differences in functionality. The only change is it being built locally by DKMS instead of coming pre-built.
It builds the kernel module for your specific kernel. It's not different from the nvidia package, that's just the same thing pre-build for the default kernel (in fact if you install both nvidia-dkms will build the module locally, then realize the exact same thing it just build is already there and move on...).
I know my Pop!_OS install pulls Nvidia drivers and modules using flatpak. I don't know the pros and cons of this method, but I've assumed it's more robust due to decoupling of dependencies.
What is your opinion on flatpak vs pacman for proprietary Nvidia drivers?