You should expect the tongue weight of the 30' Classic to be at least 1100#, and very likely more.
Look on the inside driver's door jamb on the Denali. There will be a yellow sticker and a listing: "The combined weight of occupants and cargo should never exceed xxxx lbs." The maximum capacity will probably be a little bit over 1500#.
Compare that number to the combined weight of your expected people passengers, dog(s), other items carried in the Yukon, the weight of the hitch, PLUS about 1100-1200 lbs. of Airstream tongue weight. My bet is that you will likely be well over that maximum listed cargo capacity.
We sold our 6 month old 2015 Yukon Denali with only about 4000 miles on it when we bought our 2016 30' Serenity because the cargo capacity was no where near what we needed it to be.
Your cargo capacity needs may be extremely low (two very light weight people, with nothing else to carry in the Yukon). In that event, you will probably be right at the maximum capacity of the Yukon Denali. More likely you will have cargo capacity needs that exceed the limit of the Yukon Denali.... but only you can determine this for sure.
BTW, we traded our 2015 Yukon Denali for a 2015 Sierra Denali HD Duramax/Allison and have been absolutely thrilled with the choice for towing our 30' Serenity. We have excess cargo capacity available if we want to carry another passenger or put on a camper shell, kayak, etc. And when it comes to climbing the western mountains and steep descents into the valleys, the capability of the Sierra Denali HD Duramax is very impressive and reassuring.
We occasionally like to camp without hook-ups and also carry a Honda EU2000i generator, a 5-gallon gas can, two camp recliners, six gallons of bottled water, leveling blocks and chocks, a tool box, and a few plastic storage containers filled with various miscellaneous items. My wife and I, together, weight about 310# and have a 100# Golden Lab pup. So, without carrying ANY extra items in the tow vehicle, we have 310+100+1100 tongue weight = 1510#. With our Denali we were at maximum without carrying ANY cargo. The additional items we like to carry put us close to 2000# cargo weight in the tow vehicle.
2016 Newmar Bay Star 3124 Class A
2015 Staffordshire/Heeler Mix ~ Kimber
2004-2016 Golden/Lab Retriever ~ Harley
2015 GMC Sierra Denali HD 3/4 ton Duramax
2016 Airstream 30' International Serenity-Recliners