I've recently upgraded from an RX 570 to an RX 6600 and while the performance gains and especially power draw are really impressive, I have been having quite a bit of issues related to the Adrenalin software.
Whenever I start recording with Relive or enable instant replay my cpu usage spikes, with the recording taking up to 15%. If I switch the codec to h.265 from h.264 the usage drops about a half to 7.5% (which would make sense). I have been having some issues with stuttering in cpu bound games (especially osu!) or dropping frames while playing youtube videos and turning of instant replay has solved these. I have checked and this is not an issue on my old system with an RX 570 - instead the gpu usage spikes up to about 75% and is categorized as gpu encode in task manager.
Another smaller gripe I have is with the performance tuning within AMD Software - whenever I reboot my custom tuning settings are not applied. I have tried turning off fastboot in the bios, however my undervolt and fan curve still dont apply - which is an issue because at the stock settings the gpu fans max out before the junction temp even reaches 70 °C (thanks msi).