@tornanti Although your card will struggle with DP XD() if it satisfies the 1GB “rule” (which it does) then it should be allowed to work at its own pace. Downgrading the product to CPU only essentially makes it useless, i.e. exporting will take forever(ish)!?
Incidentally is your GTX750Ti a 2GB model or a 4GB model?
Another user chose to look at upgrading and encountered the increased power requirements demanded by even a modest RTX card and the final bill comes to more than was originally hoped.
However, such upgrades should be in the users control and not forced on the users by faulty software and for laptop users it will mean a complete machine replacement.
The current faulting of 2GB cards is a bug @DxO_Support-Team which needs to be fixed, preferably with an extension to provide an option for DP XD to all users, alongside DO XD2s, to remove the performance penalty associated with DP XD2s for certain GPUs which meet the imposed 2GB rule (sorry 1 GB rule) but fail to have some other characteristic(s) of the RTX range.