Which part to upgrade for smooth playback?

I am not getting smooth playback in DaVinci Resolve (especially with 60 fps video) and I figured it might be because of insufficient power on my PC, specs below. What part(s) would I potentially need to upgrade in order to achieve smoother playback? I presumed it might be because of my HDD and slow read speeds.

PC Specs:
AMD Ryzen 3 3200G
Radeon RX 580
MSI b450m pro m2 max motherboard
Seagate Barracuda HDD (1 TB x 2)
16 (8 x 2) GB 2666mHz RAM

Studio or free? Timeline in UHD or HD?

What kind of media?

What part(s) would I potentially need to upgrade in order to achieve smoother playback?

Buy a really large size SSD so you can generate lots of optimized media

Resolve can't do smooth 60fps on 60hz panel due to vsync quirks. No amount of hardware can fix it.

Studio or free? Timeline in UHD or HD?

I have the free version. Timeline is in HD.
(Sorry for the late answer)

So, if your sources are H264/265, either transcode or get Studio.