DaVinci Resolve v17.1.1 Painfully Slow and Stutters

I've been using Davinci Resolve for a few months now, just got the Studio version recently, but I noticed that when I try to do any 'complex' work like adding a few Nodes in the Colour Page, and/or do something with Fusion, the playback gets painfully slow, sometimes playing at around 5 frames per second, which makes it hard to do any editing. I've been using the Proxies / Optimized Media etc, and maybe the only thing that helps sometimes is "Render in Place", but it's hard to test things like a Fusion clip without spending ages rendering etc.
My PC specs are fairly good:
DaVinci Resolve Studio v17 (latest build)
AMD Ryzen 9 3900X 12 -core processor
NVIDIA GeForce RTX 3070 with the Studio driver (latest version)
32GB RAM
SSDs x 2
I noticed yesterday that the SSD, CPU and GPU were hardly being used much, maybe around 20%, when trying to play a Fusion clip (which was heavily stuttering), although the RAM used was around 28GB.
Otherwise I don't have a clue why it stutters and plays at around 5 fps?
I haven't noticed much of a performance differences between the Studio version and the Free version either...hoping someone can shed any light on this?
My PC specs are fairly good:
DaVinci Resolve Studio v17 (latest build)
AMD Ryzen 9 3900X 12 -core processor
NVIDIA GeForce RTX 3070 with the Studio driver (latest version)
32GB RAM
SSDs x 2
I noticed yesterday that the SSD, CPU and GPU were hardly being used much, maybe around 20%, when trying to play a Fusion clip (which was heavily stuttering), although the RAM used was around 28GB.
Otherwise I don't have a clue why it stutters and plays at around 5 fps?
I haven't noticed much of a performance differences between the Studio version and the Free version either...hoping someone can shed any light on this?