X550-T2 PCIe x4

It depends; is your PCI-E 4x slot version or version ? If its version then you should be able to run anything up to a 9600 GT in

PCIe cards can always operate in PCIe slots with the same or more lanes than the card For example, an x8 card can operate in a slot with x8, x16, or x32 lanes

4x8 slot car layouts PCI-e 4X PCI slot expansion box is designed to expand from an existing PCI Express slot on your computer system The PCI Slots are plug and play expansion

4x pcie slot The X570 TUF does not come with an X4 slot and I'm not sure if I'll be using the second PCIE X16 slot for something else 4x card directly at