Also understand the good feeling of KISS
! But, also are in the group that suggest you not worry about the slide too much. At least one in the living area can make a big difference.
On our quest for KISS, we looked specifically for a non kitchen slide unit. Yes, KISS-able in that no moving plumbing. But more for the added cabinet space, as with slides you can lose up to 6" of headroom storage. Our current coach, we added a third shelf into two of the kitchen cabinets, about 7" down from the top. Stash lots of thins we don't use often in these shelves, and still have had no impact on tall item snot fitting on the shelf below.
We also wanted to have slides only on the Driver side. One reason was the PITA of ducking under slides to get things out of the basement, the other was that though slides do take up more space in a camp site, by having only one side with slides, we minimize that total width. (Some of our local area favorite campgrounds, have sites from the old trailer days, and not too wide
IMO, set your budget, and drop years to obtain a higher up the good chain coach. Save some budget funds to possibly 'refresh' the items in the coach that may not be what you like (add new TV's vs Tube; change out carpets if needed; maybe adjust cabinets to your needs, etc.). At the length your looking, and amount of planned usage forecasted. A gasser vs DP conversation can be pretty short. That being said, if you plan to hang onto this rig along time, then 'usually' the higher quality units are DP.
In non slide, that I do not recommend - but heck, your choice for sure
! Consider and old Bluebird or Wanderlodge. They have the length, built like tanks, and many owners go thru them with great detail on 'refreshes'. And, as mentioned earlier, Foretravel has some non slide units in the length you mentioned. And Foretravels usually have larger engines, ISM or even M11's in the older units, and the Allison Retarder transmissions are nice. Both Blue Bird 'Bird's'/Wanderlodges and Foretravel are solid coaches, that will provide decades of usage.
On the slide side of things, consider some of the smaller Country Coaches (Allures can be found at 32', 34' and 36', and are a good bang for the buck.
In a gasser, I like the Trek's, but would get one without the diesels, leaning more towards the 8.1 gasser models.
Good luck on your quest, have fun,