There doesn’t seem to any negative side effects so far (aside from fan noise) but I was wondering why when an empty scene, with just a cube, renders with such different usages.
HDRP - standard project template - OutdoorsScene
No lighting/volume/environment changes. No terrain. Just a cube.
standard GameObject: Task Manager reports ~10%.
Adding Entities Graphics package to project: 35-40%
Actually placing cube into SubScene: 50%
These numbers are while the Camera is idle, no animations playing and no physics. On an i7 12700F and an RTX 3060ti with 32GB of ram and a 1tb nvme. When I open up virtually any other game I have on my steam account, CPU usage is nowhere near these numbers. Especially when the game is idle.
That being said, I can keep cramming lots more entities into the scene and CPU doesn’t change a whole lot, on the higher end it can idle around 60% usage. Still really high though imo.
V-Sync didn’t seem to make a difference aside from taking up more of the frame time. Lighting and Quality settings all turned down to low or medium. No global illumination. No screen space anything.
Anyone know what’s up with this?
My fans get fairly loud when I run the standalone player build. I’ve been having a lot of fun writing ECS systems and not looking forward to rewriting the hybrid renderer to bring these numbers down 
[Edit]
I get the same results on Unity 2022.3 2023.2 and 6preview