BLUS31197 Drakengard 3 low performance

Try changing the following settings:

Preferred SPU threads to 2 instead of 1
Enable SPU loop detection
ASync with Shader Interpreter

Otherwise your settings are pretty much correct. You shouldn't be losing much performance if any when scaling to 1080p from 720p with those specs. Ultimately, you can try rendering at 900p and using FSR to upscale to 1080p with RCAS 50% or 90%.

Note that even with a good CPU, you will find some frame drops below 30 FPS as the game is poorly optimized, I get some even with my 2700X (e.g. on the beginning, when the dragon comes down to throw some flames).