In BIOS there is the DVMT option to select - DVMT or Fixed,
Which is better,
It depends on whether you have integrated graphics or dedicated graphics card.
1. Dedicated graphics card: ignore it
2. Integrated graphics card: use DVMT, in integrated graphics it shares your system memory to use as video memory. DVMT is a method where the video card uses your system RAM as efficiently as possible. DVMT can dynamically allocate your system RAM(capacity, and bandwidth I believe) depending on the programs you run.