I know, I had the same problem. I use my old Sapphire Fury Nitro.
My workaround was to clean uninstall the drivers I used (19.2.2) and I installed 18.10.2. More than a month with them and I have no problems at all with wattman.
A friend of mine tested the 18.11.1 for a couple of weeks now and said they are stable too. I may give them a try but I am not going to surpass those drivers for quite some time now, unless they are going to fix that annoying problem.
With the "wattman" problems, if you are in a gaming session (pubg, fortnite, lol, hots etc) the only "solution" is to reboot your pc. This is not an option for me, as you are losing those games 80% of the time if that happens and It was happening at least once per day. So, I am staying with the old tested drivers 18.10.2 to have my head clean from troubles...
I hope to fix that annoying problem soon. Maybe they can disable the wattman temporally in some drivers...
My advice to you: if you have not tested the 18.10.2 or the 18.11.1, then try one of those and check things out. In any case, I would appreciate if you could share your findings here in forums.
Friendly
Jimakos Bilakis