SeeMTA V3
They have a customizable UI and it has one that shows VRAM usage, which is usually 1GB with normal textures, and 1,4GB with HD textures. I use the normal textures.
The game also shows that it finds 4GB's of available VRAM. My card is an 8GB model, but that could be because of MTA's limitations. No idea.
Title says it all. My game randomly crashes every 30-60 minutes. Sometimes I have to shut it down in task manager, sometimes it exits automatically. I've reinstalled MTA since then, the crashes still occur. A few months before I had kind of the same problem, but back then my screen started "flashing" as in my character and some assets in game started disappearing and appearing, same can be said about my HUD.