First of all, congrats on your purchase and welcome to Tug

!
Since it will take about 2 months before Marriott recognizes you as the new owner, take the time to read lots of posts here so you get a better grasp of trading and trade value.
That said, there are no cut and dry answers to your questions and you are likely to get lots of opinions as to what to do. You can see which weeks are the best to reserve by looking at the
demand index in II (click on the link for travel demand index); that gives you a general idea of which weeks are most requested for the travel region. Try to book one of the higher demand weeks, keeping in mind that school vacation weeks and holiday are likely to give you an edge.
You will get great trades with this unit. If AC's are being offered for the week you book (and you can check with the Marriott II desk and ask which weeks AC's are being offered for before booking, btw), they generally will be offered for either the 2 BR or 3BR unit; AC's are not offered for the studio portion. Unless I am mistaken, the unit locks off into a 2BR and a studio unit.
As for whether to deposit the 2 BR or 3 BR for exchanging- that is the more complex question. It depends upon what you want and when you want to go. For example, you mention Hawaii- if you are looking for a 2BR exchange during a peak time of year, then I'd deposit the whole 3BR to maximize your trade power (II considers resort quality, desirability of week booked, and unit size when determining trade value, as well as how far in advance the deposit is made). On the other hand, if you are looking for an off peak week (even though Hawaii is Platinum all year, there are certainly weeks more in demand than others) or a 1BR or even a studio unit, then certainly lock off your week and enjoy 2 trades for the year (possibly a third if you get an AC). So, whether you should lock off before depositing depends largely on where and when you want to go; if it is a big trade up, so to speak, I'd use the better trade power of the entire unit, but otherwise I'd maximize my value from the 3BR purchase and split the unit.
Also- if you can make travel plans relatively last minute, within 59 days before travel (Flexchange) your studio can pull anything that your 3BR would- so you can get 2BR units even from the studio trade).
Don't forget- whatever you do- book the week with Marriott directly before depositing to II.
I think the 3BR units offer a lot of value for use and trade. Plenty of space for an extended family trip or with friends if you use it, gives you an edge when trading it to get those high demand weeks (such as a 2BR Hawaii or Hilton Head over the summer, a winter Caribbean week or ski week, etc), or the trade power of a 2BR with an additional studio week for a MF of just a few hundred more a year. You got a great deal to boot!