I have 2 monitors Gigabyte 27", 2K, works flawless, on 144 Hz. Is stable for me with 7,1 definition, no WE enabled, and pikera as boot arg. Both monitors on DP port, since the HDMI I use for a 21" graphic display pen (works also fine is seen as 3rd display).
Oh interesting, no WE.
I'm kicking myself (a little). I have a 6800 (non-XT) sitting here for months, waiting for support. I've been running a Sapphire 5700 XT in a new build since last summer, but ever since 11.3 have been dealing with green screens multiple times per day (like 5+). This week, because I couldn't stand the green screens any more, and didn't know if 6800 support was actually ever going to come, I dropped US$410 on a used RX 580. Running blissfully stable.
Guess, I'll try the 6800 now, for a few days, and if it is stable, sell off the RX 580 and 5700 XT.
Thanks for the quick feedback on the multi-monitor, I've got dual 4K's that I typically run at 3008x1692.