I don't have A1111 but in ComfyUI using a shared workflow that does base and then refiner, SDXL 0.9 was using 12GB of VRAM and 22GB of ram in Ubuntu for me.
Doing images of 1024x1024~
GPU: AMD RX 6800
Also using Comfy. Have been able to get away with 6GB of VRAM doing 1024x1024 and it took a bit longer but I've done a couple of 1024x2048's and they're coming out good :3