I've tested the various disabling options.
"Disable transfers for career" seems to only affect the user not the CPU.
"Disable first window" works similar to FC24 where no transfers take place at all. However, there is currently a bug where the CPU can sign free agents.
Temporary quick fix for this is to go into edit teams in the main menu, search for the free agents, and just manually transfer/dump them in a league that won't affect your competitions. I play premier league teams, so i dumped them all in the Saudi League so no English/European teams are affected.
Hopefully bug is fixed soon though.
