Does the OS slow down from an external hdd?

Question

macOS

Hello. I'm going to buy a macbook, but the memory is not cheap there, so I need an external drive. I plan to put windows there. And of course, sometimes you want to play. Actually, this question is: will fps differ much in some games if there is an hdd, or will you still have to spend money on ssd?
PS I understand that the macbook is not for games, I do not take it for this)
Thank you in advance for your answer.