Absolutely! You can have up to two waitlists at a time so you can waitlist for a studio and a 1BR. Remember that a waitlist must become fully available in order for it to fill. This means that if you need 7 nights and, say nights 1, 3 and 5 are available, your only option is to waitlist the entire week. This is because you cannot waitlist the nights individually due to the 2-waitlist limit. However, if you waitlist the entire week, they do not hold nights 1, 3 and 5 until the others become available. So someone could snag up the available nights before your waitlist fills. This is why most people suggest that you book what is available and waitlist only those nights that are NOT available, subject to the 2-waitlist maximum. Another option is to break your stay into parts, having 2 waitlists of 3 nights and 4 nights, instead of a full 7 nights.
Another thing to remember, watch your banking deadline and waitlist expiration. If you have a studio booked and a 1BR waitlisted, and the reservation is in your current UY, but AFTER your banking deadline, be careful. At your banking deadline, you will have two options: bank the points that are not tied up in the studio reservation, OR don't bank them and risk losing them if the 1BR waitlist does not fill. But remember, if you BANK them and the 1BR waitlist DOES fill, they will borrow points from your next UY...NOT the ones you just banked. This could have an impact on your future plans.