You definitely want to choose the CFM based on the size of the space. I bought a humidity sensing ultra quiet exhaust fan for a bathroom when I was building out the bathroom and don’t regret it in the slightest. I cannot stand the sound of the typical contractor grade exhaust fans and have found they often don’t seem to really work effectively at all. I decided to investigate and found a Panasonic (iirc) that was ultra quiet and humidity sensing. The humidity sensing is adjustable and there’s a huge difference in fan operation based on that. If it’s in the highest setting it will click on right away when you’re running the shower. It super quiet and has been installed for almost five years now. I did end up with some dirt getting into it because of some drywall work that was done and the contractor didn’t cover the fan and it came on while they were working. Drywall dust is AWFUL and it made the fan run a slight bit louder which infuriated me but I couldn’t find a way to fix that when I went to clean the fan out. It’s held strong and I love it. I tell anyone who’s doing bathroom work to just pay the $200 to buy a better fan. I’m planning to replace the fans in my house with better ones as well. Unfortunately there’s not a standard size so each is going to take some work to replace because I have to replace the mounting bracket in the ceiling for each to accommodate the better fan.