The 3 worker limit would require you to get creative to obfuscate Roblox’s arbitrary limitations.
I say arbitrary as any official documentation and comments from Roblox staff regarding this limit is incredibly sparse, and any request for comment gets ghosted by staff.
There is an engineer that responded here by essentially saying (And I paraphrase):
The system works, and it could definitely take advantage of the hardware, but we won’t publicise information that may change on-the-fly.
Personally the philosophy of writing parallel code is to ensure that you can maximise the performance out of the hardware you are running it on. It could be that Roblox is holding back the worker limit to retain parity with lower-end mobile devices so developers don’t end up making games that become too demanding for them; however this would be a fallacy since this kind of bottlenecking is already possible (And much easier to accidentally do by developers) by stressing out the GPU.
So if I was to make use of the renderer in its current state while upholding the 3-worker limit, I would disable both Global Shadows and Light Shadows, and set my game to take place at night/dark setting; perhaps taking advantage of horror-type games lending itself well to low resolution content.
(A relevant example of this combination would be REPO)