Question about how big should streaming textures memory pool be for specific hardware

Hey there everyone, I was wondering if anyone here can tell me how big should the streaming memory pool be for specific hardware configurations. I have seen a lot of answers to the effect of “oh, just make your memory pool bigger”, or “use less textures because you have gone over your memory pool”, but I am looking for actual numbers.

So first off, should your memory pool be set to how much VRAM is on your graphics card? I know there is more than just texture that use up VRAY, gBuffer / shadow buffer / resolution / etc, but I have also heard that the memory pool can be set higher than what is on the graphics card as system RAM is also taken into consideration, is that accurate or false?

Example, right now I have my memory pool set to 7000 on a system with a GTX970 4GB card, and 32 GB of system ram, is that too high? Should I set it to 4000? For systems with 2GB VRAM graphics cards should I set the memory pool to 2000? or 3000 or 4000 do to the use of system RAM also?

Or should I set my memory pools lower than what is on the graphics card because things like frame & shadow buffer use VRAM also?

I am not having any problems yet as I am only using about 2000 of my 7000 pool, but I still have lots of stuff to add to my scene, and I am working on a settings menu with different graphical settings for cards with lots of VRAM, and different settings for cards with less VRM and I am trying to get an idea of what those settings should be.

Any insight on this would be most appreciated - Thanks!