Welcome and congrats on looking for a tt!!!!
Floor plan wise, it all comes down to what will work for you. Some people will stop and make lunch while traveling, others stop at a restaurant and won't get in the camper until they arrive at the cg.
But a 1500 Subruban towing that trailer, you are definitely going to be over a lot of the ratings as other have stated. What year is the Burb? If a '06 or newer (I think it is), there is a yellow sticker that states "All passengers AND cargo not to exceed XXXXlbs..." (Something like that!), what is that amount??? Regardless of how much it is, that is the weight that is stated by GM that your Burb can safely handle. That weight is all the passengers, any coolers, bags, electronic devices, and accessories added (step bars), AND the trailer tongue weight. As mentioned, that trailer could have ~1200lbs tw (tongue weight), which most is "carried" by the tv (tow vehicle). Follow the links in my signature to understand how a wdh (weight distribution hitch) works, how to set one up, and how to weigh at a CAT Scale to better understand all the dynamics involved in towing. Just because your Burb is rated for xxxxlbs towing, there are other variables involved as well that will limit the actual total trailer weight.
Make sure you do get a good wdh with integrated sway control. The Reese Dual Cam, Teese SC, and the Equal-I-Zer 4 way system are all very good ones. The DC (Dual Cam) is a little more finicky to set up, and if the tw changes a fair amount (fresh water tank full vs empty unless over axles), but very good. The SC and 4 way are very similar. The Reese hitch head (same for both models) will allow a little more fine tuning for the wd bar adjustment thah the Equal-I-Zer hitch head. But you can't go wrong with any of these models!!! Make sure you get all the paper work with the hitch. And most importantly, the proper size rated wd bars!!!! If the trailer has a "brochure" tongue/hitch weight of say 900lbs, do not buy the 1000lb bars!!! The actual loaded tw will go up. The manufactures don't even include the weight of the propane tanks or a battery on the tongue in the "brochure" dry weight!!!
While calling GM is a start, the people on the phone only know the "tow rating", and may not understand all the other variables that should be taken into account to figure out a properly size trailer for your particular vehicle. And the rv dealer sales person..... as mentioned, all they see is a sale!!!! I should say most of the seals people only see a sale!!! There are a few out there that do understand and care only selling what you can safely tow.
Good luck!!!