Do Thunderbolt ports in Surface Pro 8 share the bandwidth 40Gbps? Or Do they have 40Gpbs each indepe

I am planning to have one port for EGPU only for its maximum performance and the other thunderbolt port for the thunderbolt dock to connect Ethernet, Mouse, Keyboard, External SSD and so on. If these two thunderbolt ports share the bandwidth anyway, my external SSD will eat up some bandwidth of EGPU. I don't want this to happen, so if this is the case I should get Surface Dock 2 instead. Anyone can give answer to my topic?