I remember seeing 100% CPU usage in apex using a i7 9700f CPU at 1440p and it would stutter, I can only imagine at 900p the load on your CPU has to be brutal.
You want the GPU usage to be high as possible, the CPU being that high is what's causing the stutter.
I ended up having to use rivatuner to cap the fps to reduce the stutter. I'd suggest trying that out at different fps to see what works best for you. Also try not to have a bunch of stuff running in the background.