2018.03.17 13:47:13 Warning - This may indicate problem with the drivers or registry or that system is not supported
2018.03.17 13:47:13 Warning - I will now stop, use Force to mod anyway at your own risk!
Should I install old 16.1.1 version?
No idea. It's just a warning anyway. Tick 'Force' and proceed.
Typically Catalyst_Version registry key is present for every AMD GPU in the system. If values don't match - it's weird, they should match.
In your case, looks like it's empty. Probably because new drivers don't have Catalyst at all.
However, mod stopped working when RX video cards came out. And Win10 supports 6xGPUs out of the box..