Enabling Resizable BAR in the computer BIOS allows the CPU to fully access the memory in the GPU card. It seems to be highly desired by those who play graphics intensive games on their computers. I don't play games, but I do a fair amount of Lightroom Classic work (masking, generating previews, etc.). My computer's BIOS, my GPU, and my OS all support this being enabled, but I have left it off up until now. If I find out that Lightroom Classic would use it, I would gladly re-enable it.
I'm using Lightroom Classic v12.3, Windows 11 Pro 22H2, CPU is AMD Ryzen 9 5900X, GPU is RTX 4070 Ti, and NVIDIA Studio Driver v 531.61.