I don't like flashing bios so I solved this problem finally.
v12.1 is almost ready, I'm going to release it in 3-4 days.
It cannot perform runtime tuning of memory timing registers, it will be added a bit later, in another update.
But it can apply entire straps on-the-fly (Windows only). Currently for Polaris cards only, may be later I will add support for other cards too. So you can use stock vbios and don't flash your cards to try new straps.
Instead, you just put new strap string to config file and the miner applies it immediately in runtime.
If specified strap is not working it will not cause any problems, after reboot you will have stock strap again because bios is not changed.
This way you can keep stock bios and also test new straps safe and easy.