At last the MAG B550M MORTAR WIFI has got the final production ComboAM4PIV2 1.2.0.2 BIOS after a couple of previous beta versions. Just installed it and it was painless. I re-entered my carefully tuned fan profiles from previously, and set 3200 XMP, and job done. Is there any improvement ? Hard to know, but I'm pretty sure there will be no need to do further updates. (probably no need to have done this one either, but it just makes me feel better, lol)
I'm simply running my 5900X at stock as I'm totally happy with the performance. The only tweak I'm thinking of is if the Corsair memory could be undervolted below the 1.35v stock value to extend its lifespan, but for now it is as it is.