I've got it a couple of days ago ( XFX 4GB version ), and while haven't yet got around to checking how are things going on Manjaro XFCE install, on Debian Stretch it runs fine with linux 4.8/4.9 and amdgpu ( non-pro ). Same on KDE Neon with latest KDE5.
1. Debian desktop wise, XFCE + xfwm4 with opengl composition = all good.
2. KDE Neon, opengl 3.1 rendering = all good.
3. I rarelly play games, esp. on Linux, however Torchlight runs fine.
4, Video accelleration runs fine ( ~5% CPU usage playing 1920x1080 H264/AVC ).
5. Power managment seems to be good. Idle temp is around 21C, fan barelly spins1 ( ~28C after 10min Torchlight session ) .
Graphics: Card: Advanced Micro Devices [AMD/ATI] Baffin [Radeon RX 460] bus-ID: 01:00.0 chip-ID: 1002:67ef
Display Server: X.Org 1.19.0 driver: amdgpu Resolution: firstname.lastname@example.org
GLX Renderer: Gallium 0.4 on AMD POLARIS11 (DRM 3.8.0 / 4.9.0-ck1-c2d, LLVM 3.9.0)
GLX Version: 3.0 Mesa 13.0.2 Direct Rendering: Yes
mpv -v --hwdec=vdpau --vo=vdpau ./Wagakki\ Band\ -\ Senbonzakura.mkv
[vd] Using hardware decoding (vdpau).
[cplayer] VO: [vdpau] 1920x1080 vdpau
[cplayer] VO: Description: VDPAU with X11
I haven't tested amdgpu-pro, however fglrx is not available for RX460.
Also, I guess you probably know, but it's worth mentioning just in case, for amdgpu you need linux 4.7 or later ( older version don't have support for Polaris radeons ).
1 Fan RPM reading is coming in linux 4.10.