What is your HP pavilon ? You can't change video VRAM both iGPU and dGPU.
(a) For dGPU: What you get is what you paid for.
Integrated video (iGPU) does not have room for keep VRAM, it relies on System. System will work this out and allocate/assign spare/available system RAM to VRAM automatically when required up to max limit. System will also take VRAM back when required (the number is dynamic, not fix). During the good old days, we could do this from BIOS but now OS is smarter.
The following document shows Max shared RAM for Intel iGPU versions
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