245/70 16 is the stock size and you'll find slightly better prices in that size because it's more common (on LOTS of older GM trucks and others). I'd shop that size and then not worry about it.
Here's what I'd do if I were you:
A) wait until October and then when GM's fall tire rebate is on, get a set of Hankook AT2's installed for about $300 OTD (Yes), with lifetime balancing/rotation/etc. Twice a year GM will give a $200 rebate on tires purchased from them if a) brand is Hankook, Bridgestone, Pirelli, Conti, Goodyear. Less rebate for other brands. Must use the GM buy power card for maximum rebate, but you don't have to pay interest. Just pay the card off when it comes. GM will price match the lowest dealer/installer price within 100 miles, so if you have a Walmart in that distance, you get their prices PLUS the rebate. Amazing deal.
B) Since they do Bridgestone, you could do Blizzaks, too. I am putting either Blizzaks or Hankook I-cept on my (new to me) Volvo XC70 to use a a ski car to go up to Snoqualmie Pass, over to Wenatchee and Mission Ridge a lot this winter (instead of the Trooper/SLX).
c) Last fall, I used the GM deal to get the Hankook Dynapro HT installed (highway tread). it was about $270 after rebate (245/70-16). Rebate was fast and painless, btw. Anyway, a month after I went with the HT, I decided to start skiing again after a big break. I started teaching lessons up at Snoqualmie Summit and was going up there three days a week. I was really hating my decision to go with the HT instead of the AT, BUT - the truck did fine in ALL conditions all winter (until Covid at least!). I was surprised. Given what you said, I'd go AT2, take the great deal, and not look back.
I did some "mild" offroading on the Dynapro HT tires this past summer. Deflated them to 25lbs and they were great on dry forest roads and some trails, like the stuff above Liberty if you know that. I had zero complaints with them. In retrospect, I should have gone AT2 and I'd be happier all-around.
If you want dedicated snows, the Blizzak is good, but know two things: 1) the soft winter compound is the upper 1/2; it gets harder down lower so once you are down to 1/2 tread they are toast for pure winter use. 2) Also, in your heat in the summer, they will wear badly and be really soft and floaty - I have run winter tires year-round before on the East coast (I used to live in NY and VT, and norther VT at that). You could run the winter tires in norther VT in the summer, but if you went south where it was hotter, they got sketchy at speed and with heavier vehicles.
Oops, just re-read and saw this:
"They will be winter only "
In that case I would get the Hankook I-cept. It's a better non-studded tire than the Hankook I-pike (a lot of gripes with them when not studded), and will give longer winter service than the multi-compound Blizzak.
I focus on Hankook and Bridgestone here as those can give you very good snow tires at great prices, and thus maximize the GM rebate and price-match. There are lots of good other snows out there, but these can be had at amazing prices. Usually the rebate period is for tires purchased 10/1-11/30 (and again march/april they do it), so I'd wait until at least the first of October to see that deal pop up. here's a link to the terms for the last deal:https://media-dmg.assets-cdk.com/teams/ ... 8ba825.pdf
It ran sept. to Nov last year, I think normally it's Oct to Nov. Also, sometimes Ford dealers do the exact same deal.