Resizable BAR is not the reason for high VRAM usage in MSFS 2024. Disabling it may reduce VRAM usage by about 0.5–1 GB (I tested MSFS 2024 with RBAR on and off), but that’s about it. It can make sense to turn it off if your GPU has limited VRAM. On cards like the RTX 4090/5090, however, there’s more than enough memory, so this setting really isn’t something to worry about.