One other thing to consider about “empty scenes” in HDRP is that they’re by no means empty.
HDRP runs a lot of upfront costs for processes into memory channels.
These costs can still exist even of the associated component isn’t even present.
Post processes that are turned on in a frame setting can still be processing even if it’s not added to a assets volume defaults of a scenes volume override.
But default HDRP assets and project settings have a “best effort” set up, but it’s always important to tune these carefully for your projects scope, even before you begin developing.
Compared to an empty built in scene running 1ms for example and an HDRP empty scene with global volumes running volumetric clouds, and all the other HDRP asset defaults in the system settings, you will get a large difference in your stock headroom available.
We covered some ** information ** on this early last year, that might also be helpful for you.
All the best.