You can also use the debugfs files, which lets you change the amount of memory each VF gets allocated: Proxmox 9.0 + Intel B50 SR-IOV -- finally its almost here! Early Adopter's Guide - #583 by mal7hael
Although I found it to be a little bit finicky - Intel Arc Pro SR-IOV: Change VF Memory Allocation | Steve’s Blog.
It also seems Intel has added vram_quota to the normal sysfs in Kernel 7.1: ABI testing symbols — The Linux Kernel documentation. But I haven’t tried it yet, since Proxmox is still on Kernel 7.0.