Do certain seat brands hurt your body to sit in?

Yes, seat makes a huge difference. I only drove Volvos and all their seats sucked until 2019. Now their seats are really good.
I managed to find myself a Recaro bus seat, it's amazing.

 

Every body is different. Lumbar supports are a major pain source for me, my back don't like being bent that way.

I bought a couple of these a while back, before the prices jumped up, for the house cause they fit me right.

Midcentury Rocking Chair by Lee Woodard For Sale at 1stDibs | lee woodard rocking chair, lee woodard furniture, leather rocking chair

 

Between Volvo, Cascadia and ProStar, the Volvo was the worst and the Cascadia the best for my back.

Older trucks for any of them were the worst, I think because the previous drivers (I'm assuming) had been much heavier than me and left the seats a bit misshaped.

Some of it could be because of the different suspensions on various trucks. Some ride softer and some harder.

Also, the adjustments you make (or don't bother to make) to the seat. Do you set it to float, or not to float? Some let you pull the bottom cushion out/forward a bit to support a longer leg. The seat back inclination angle is important. The angle of the bottom cushion can also make a difference, as do the various air adjustments for lumbar support. Some seats have air adjustments for two or three regions of back support.

And while not exactly seat related, the position of the steering wheel also figures in to finding that perfect driving position for comfort.
Up, down, forward or back... a quarter inch in any direction can really make a difference.

If you are just hopping in and driving without learning and using the adjustments available, you are doing yourself a disservice.

 

Oh, don't complain, this is all we had, thank God it's no longer available.
https://seatsrus.com.au/product/bostrom-biking-bar-seat-mechanical-no-longer-avail

 

I don't know the brand, but it was the seat in a 2020 and 2021 brand new Freightliner Cascadia. I've Sears Roebuck seat. It had a flat bottom cushion and flat back cushion in a heavy-duy synthetic tweed cover. I never even considered or wanted an aftermarket seat bottom cushion in any Peterbilt, Volvo, Sterling. I HAD to find a seat cushion to keep driving the Freightliner. All truck manufacturers have good, better, best type seat options. I used an aftermarket or home-made lumber cushion in every truck I drove and fanatically focused on sitting straight upright to prevent back pain. Slouching, even a little, all day will wreck your lower back eventually.

 

Most of the time for my body aches while driving. I can reduce by adjusting the seat. Not so much as to the brand of seat.
One truck I drove the adjustment of the steering wheel is what reduced my discomfort. Another I stopped using the arm rest on the right arm side.

 

I had a legacy seat, it was hard and I never liked it. I only bought it because a got a really good deal on it. It was cheaply made in my opinion, and the fake leather started cracking.
I bought a Vandetta Seat and I love it! I bought it at Horse and Buggy Accessories and got it at a very good price.