We have many machines at our office with almost equal specs as you, PeterPan1973. We're at ~30 fps in Europolis, ~60 fps in Storytime, ~30 fps in Friar's Keep (I don't know where you're at in the game so just listed some scenes for reference).
12% CPU usage seems very low, at least if you're in Europolis, which is the heaviest scene of the game. I'm personally running the game with 40%-50% CPU usage.
Rendering in Unity is CPU-bound, so you should see a higher CPU usage than 12% at least.
With regards to the executable being 32-bit; this is because there's a bug in Unity where random crashes occurs on 64-bit standalone builds. This bug is fixed with the latest patch of Unity, which we've tried implementing.
However, this patch unfortunately introduced other bugs, which means we could not apply it to the game. Until it is fixed properly, we have to build 32-bit executables only.
Are you sure you're not running some third party tools taking control of other applications? Are you overriding graphics settings from your Nvidia Control Panel?
What other programs are you running alongside the game? Anything that uses a lot of CPU, which in turn decreases the available CPU processing for the game?
Any settings limiting usage of CPU or multiple cores?
You'd also might want to try to reconfigure some of the in-game settings to see if enabling/disabling any of them makes the experience better. However, with almost equal hardware, I'm more than able to run the game with the best settings possible.
Sorry I can't help you with anything more than this at the moment. It does seem like an odd issue, one that we haven't seen ourselves. Anyone else having/have had this issue?
I'll make sure to update you if we find anything that might help with your problems.