ConnextX-5 SFP for 25Gbps and 100Gbps

I want to use a mellanox card for incoming traffic and another one for outgoing traffic. They must be directly connected port to port to another server with X-5’s as well (see picture)

Which SFPs shall I use to have 25Gbps in each direction?

Do I even need 2 X5 in each server or can I use the 2 ports of the X5, one for incoming and the other for outgoing traffic?