How free is AMDGPU in regards to out-of-the-box experience?

[auspicious at inventati.org]

Dear mailing list subscribers,

I hope this is the right place to ask because I was unable to find any 
other mailing list. Currently I am using an NVIDIA GTX 980 Ti and either 
the proprietary driver has to be used to get any 2D / 3D things to work, 
like showing the operating system at all, or proprietary firmware has to 
be loaded in combination with nouveau (which I have no experience with).

I want an out-of-the-box free software driver experience with no 
non-free mess.

Will AMDGPU provide this? Do I need to mess with non-free firmware 
stuff? What is the highest end AMD card to combine with AMDGPU? Right 
now I am quite comfortable with Debian testing which has Linux kernel 
4.6 in use.

I am looking to play modern Valve games at highest performance. Low 
settings is usually preferred at 1280x1024. A stable 240+ FPS on games 
like Counter-Strike: Global Offensive is welcome to prepare for native 
240 Hz monitors that are coming out this year.

Sincerely yours,
Fred