Both the RTX 4070 (short card) and the 4070 Ti (full length card) have 12GB VRAM.
I have the the short card and it is fine in MSFS 2020 at 1440p resolution with DX 12.
Max VRAM usage so far is 8.5GB sans any addons.
Computer: Dell XPS 8950, i7-12700, 12GB ASUS RTX 4070 dual BIOS, 32GB DDR5 at 4400MHz, 7130MBps SSD, PCIe v4, 1000w PS.