Vram is totally different from System ram so you can use a GPU with what ever (G)DDR you want regardless of what the board uses as system ram!
Basically a video card with (G)DDR5 will work fine in a motherboard that uses DDR3 system ram!
Indeed, there is no DDR5 RAM for the RAM memory slots. You ment GDDR5 memory. This memory is actually a faster version of RAM and you can find it on graphics card, known also as VRAM . Which means RAM on your motherboard supports DDR3.