Your big concern with the setup, I think is that you want to have an in and out fan beside each other,
Your best bet will be to pipe in the outside air to the back side of the room.
You could likely run 2 5" dryer liners in over and down the back wall, and get away with a large exhaust fan.
As for the CFM you are after, you will never get a silent version. That's going to be hella noisy lol
Yes let me just explain to my landlord why i want to take down a wall from his apartment so i can have two windows

And i never said silent, two box fan at full speed arent silent at all and the CFM is plenty, they just dont have enough pressure so a bit of wind and BAM they basically stop their spin. A metal equivalent with more angled blade would be quieter, but much more performant!
I'm sorry did I say take down a wall???
If you are going to be rude, read the fucking comment.
I said pipe the fan for intake an exhaust to different parts of the room.
That's a matter of running a line, not using a second window.
I also stated use a furnace fan, but I see you thank someone else for that.
I'm done helping.
Good luck