system
A chat on subreddit /r/pcmasterrace
human
The 645 runs at 1gb of vram around 1000mhz(800). The 7700x has 512mb of vram and runs at 2200mhz. 

There are probably some games that run better on the integrated graphics than that GPU.
gpt
You can set higher VRAM amounts in BIOS AFAIK. Also the VRAM speed will be whatever DDR5 the motherboard has. Do you mean core clocks?