Does it fit RJ45 port?

No, this X520-10G-2S only has dual SFP+ ports. If you need RJ45 port network card, you can buy X540-10G-2T throughhttps://store.10gtek.com/10g-network-card-dual-rj45-port-x8-lane-intel-x540-t2-equivalent/p-8483