Does the data type effect SQL's performance? ...I have a table that has around 300 rows. About 25 of those rows are varchar(max). Most other rows are varchar(XX) and BIT. Does the data type matter at all? ...I'm still a SQL noobie.
It can to some degree. I’d focus on modeling the data appropriately. If that means you have a lot of NVARCHAR(MAX) columns, then so be it. If you find performance is an issue, then you can look at breaking those column out into another table. But, I’ve seen tables with millions/billions of rows that perform just fine, given the right indexing.