After upgrading from Intel too AMD did you do a fresh reinstall of Windows?
Is Windows updated to the latest build?
Have you installed the Ryzen chipset software driver?
Is the motherboard bios firmware up to date?
Have you tried resetting bf5 game settings to default?
Have you reset NV control pannel to default and only enable. Max. Performance option under power settings?
Is physX set to GPU modus?
Do you run in fullscreen or desktop mode?
Try a 64 player MP game and try again?
For gpu utilization please make a clear extinction between %memory use and gpu activity! A strong CPU should not run at 100% for days on end for a single process.
What framerate are you getting on sp and mp games?