The compatibility error is that the B450 motherboards usually don't come with a bios that supports the latest AMD Ryzen cpu's,the MSI Max version however does support these from the get go.
And even if not does it have "usb bios flashback" where you could update the bios without even needing a cpu or ram in the motherboard.
You can of course look for a different case if you like. Maybe there's something you like better.
If liking this one would i put the added Arctic fan in the back and relocate the fan there to the front next to the one already there. The two fans that come with the case migth do the job,but adding a decent fan for $5,- (or two) is imo a good thing.