The memory that is on a graphics card is irrelevant to the rest of the system.
Only thing you need to concern yourself with is the physical space for the GPU in question and enough power to run it.
You need an available PCIe x16 slot running at at least 8x, preferably 3.0, but 2.0 will do.
RTX2070 = 175W = 8-pin (or dual 8-pin)
RTX2080 = 215W = 8-pin + 6-pin (or dual 8-pin)
RTX2080Ti = 250W = 8-pin + 6-pin (or dual 8-pin)
Connector requirements will depend on model, and how overclocking friendly they made it on the custom PCBs.