Can you get rid of the ATI settings entirely and set the GPU to compute with a third party tool (I don't think OverdriveNTool does it)?
Yeah, just unpack driver that you want to use, install said driver via device manager (RMB on gpu > update driver > browse my computer > choose path where you unpacked drivers (\Packages\Drivers\Display\WT6A_INF) > install) or via pnputil /add-driver <\Packages\Drivers\Display\WT6A_INF\C0324065.inf> /install
Activate compute workload via registry ([HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\0000] 0000 for first gpu, 0001 for second, etc. key name is "KMD_EnableInternalLargePage"=dword:00000002)
There was a tool written for same task on this forum, but simple batch script will suffice, if you don't want to do in manually. I mean even simple reg file will suffice (example for 6 gpu):
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\0000]
"KMD_EnableInternalLargePage"=dword:00000002
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\0001]
"KMD_EnableInternalLargePage"=dword:00000002
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\0002]
"KMD_EnableInternalLargePage"=dword:00000002
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\0003]
"KMD_EnableInternalLargePage"=dword:00000002
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\0004]
"KMD_EnableInternalLargePage"=dword:00000002
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\0005]
"KMD_EnableInternalLargePage"=dword:00000002