Fabinho is likely a 35 to 40 M and Silva is a 60 M player at this stage. Monaco (like OL) is a tough team to deal with. Look at their last big deal, Martial (60 M, potentially 70), James (80 M). If you ask me today to pick between James and Silva, I will take the Portuguese.
Ox: Lacks positional discipline and more importantly he is not good enough technically. He would not start in CM for Jardim (he would even put Moutinho before him) and on the wings Lemar and Silva are one step or two above him.
Martial was 30 million rising to 60 million based on add ons. I don't see why we couldn't do the same. Ox doesn't lack positional discipline. He covers and makes tackles where he needs to. There is no reason why he wouldn't flourish in a system that relies on physicality in midfield.