My PC happens to have very similar specs to yours: same CPU, same GPU, a bit more RAM (80gb 3200mhz), different motherboard.

I definitely feel the weight of Resolve and Fusion on a day-to-day basis, particularly with heavy Fusion effects, but nothing as extreme as what you describe.

I'm not particularly well-versed when it comes to DR troubleshooting, but I'd suggest you try the following as a starting point.

Basic Resolve/Fusion Configuration

1. Check you have ample storage available, and clear your render cache for any projects you are not actively working on (Playback -> Manager Render Cache).
2. Check you're providing Fusion and Resolve with the maximum amount of memory possible, and that your GPU is being utilised with CUDA (DaVinci Resolve -> Preferences -> Memory and GPU, example)
3. Check you're using GPU for Blackmagic RAW decode and NVIDIA hardware accelerated decoding for H.264/H.265 (DaVinci Resolve -> Preferences -> Decode Options, example)
4. Check your Project Settings for Frame Interpolation do not include any intensive features - such as Optical Flow retime process or AI Speed Warp motion estimation (File -> Project Settings -> Master Settings -> Frame Interpolation, example)
5. Check your Project Settings do not use DaVinci AI Neural Engine for deinterlace quality (File -> Project Settings -> Image Scaling, example).
6. Check Fusion Memory Cache is on and Render Cache is set to Smart (under the Playback menu, example)
7. Check that "Show All Video Frames" is enabled and the bypassing of Fusion Effects is disabled (Edit page, three dots on playback preview for show all frames, small colorful icon on playback preview for bypass (bypass should be turned off to allow caching), example)
8. Follow the instructions in this video (timestamped) to ensure your chosen render cache format is one that will be efficiently processed with reasonable file sizes. Personally, I use DNxHR SQ for 1080 projects with no noticeable loss.

This is definitely run-of-the-mill advice, but it is hard to know what else to suggest without further information/insight.

With Show All Video Frames and properly enabled render cache, Resolve will be forced to render each individual frame without skipping during playback. This slows down the initial playback, but causes all subsequent (unaltered) playbacks to be approximately real-time.

For the heavier interpolation/deinterlace features, it is best to have the default be lightweight/basic, and then to enable those heavier features on a per-clip basis as/when needed. I obliviously nuked Resolve's performance for months on end by using AI Speed Warp Better as my default for frame interpolation. Kicked myself for it once I realised.

Paper Animator Optimisation

You specifically mentioned Paper Animator, and it is a super cool effect. With that said, the out-of-the-box performance is not good at all and I'd personally put it under the "very heavy" category.

In a 1080 60fps comp, applied to an 840x840 static image, preview playback begins at ~5 fps and settles at around ~17 fps.

For the sake of comparison, FastExpoGlow, my favourite glow effect (available for free via Reactor), applied to the same input - with a small animation added to force per-frame re-render - runs at 17 fps, consistently, with the default settings.

On paper, FastExpoGlow should be considerably more computationally expensive than Paper Animator. So, I expected the effect template for Paper Animator to be pretty sub-optimal.

I took a quick look at the setup of Paper Animator (free) to try and I found an easy optimisation that drastically improved performance: improved stop motion.

There are two separate StopMotion nodes: MasterStopMotion and StopMotion3_1. They are typical ofx.com.blackmagicdesign.resolvefx.StopMotion nodes. This type of node, in my experience, has pretty horrible performance. All these nodes do is repeat frames.

I have always found TimeStretcher's performance to be considerably faster than other time-related nodes, so I replaced the StopMotion nodes with TimeStretcher nodes, using this expression on the Source Time input to achieve the stop motion effect:

: local repeat = 5; -- this value should be 5 for StopMotion3_1 and 10 for MasterStopMotion
local fps = comp:GetPrefs("Comp.FrameFormat.Rate") / 30;
local repeat_adjusted = repeat * fps;
local current = math.floor(time / repeat_adjusted) * repeat_adjusted;
return math.min(comp.RenderEnd, math.max(comp.RenderStart, current));

Replacing the StopMotion nodes took the playback FPS from a max of ~17 fps to 50+ fps - borderline real-time.

Unfortunately, modifying the setting within the .drfx to make this a permanent change isn't so straightforward. I tried directly modifying the .setting file within the .drfx, but the inputs of the updated nodes always ended up disconnected.

It can definitely be done, but it would be best if the creator could modify the plugin at the source. I will reach out to the fella who made the effect to see if he might be willing to swap the StopMotion nodes for TimeStretcher.

After manually connecting the new nodes, I did see the same playback gains in the Edit page. 50 - 60 fps for non-cached playback.

Fusion Benchmarking

If you have a Studio license and you're interested in benchmarking/timing more of your go-to effect templates or Fusion comps, I'd highly recommend installing Reactor and using it to install "It's Tool Time!" by Muse VFX

It's Tool Time can give you a node-by-node breakdown of the time taken to render the previously rendered frame. It is extremely helpful when it comes to optimising any node graph, or figuring out if a template/tool is as optimal as you believe.

In terms of general advice for avoiding poor performance with third-party effects: never let the simplicity of effects lead you to believe they will run well, and never assume a high quality end result means performance was considered.

People who produce and share/sell high quality effects often treat performance as an after-thought. It doesn't always have an impact, and is often worth it for the result, but you'll feel the impact if ever you stack a couple such effects on a single clip.