Is it really better than Apex and some of the other premium TSS loads ? My Browning 10ga is back at Browning for a Duratouch warranty claim so I pulled out an old 20ga NEF single shot to use this year. I sent it to Sumtoy customs and had the barrel threaded and one of Williams fine chokes installed, I also drilled and tapped for a scope rail. I’ve added a Vortex red dot as well as a synthetic stock and forend. I spent most of the day yesterday trying my hand at camo painting using stencils trying to achieve Bottomland camo. It turned out decent but the colors are a little lighter that I’d liked. As you can see I’ve spent a fair amount of money and time on this back up gun project so I want to get the best ammo possible for it. I guess my question is has anyone here used Pendleton 20 gauge tss and how did it preform ?

I'd probably stay away from their true Magnum load... unless you like that kind of thing! I've not used it, but have heard good things about it.

https://pendletonammunition.com/shop?cat=tss-turkey

I shoot a 20ga Stevens with the stock factory Extra Full choke, OTW reflex sight, and I patterned it with Apex 3” TSS 9 shot. Unbelievable tight patterns, I would not pass up a shot at 50yds if the right situation arises.
I have never used Pendleton shot, but there YouTube vids make them look comparable to Apex loads.
It shoots so well I have given up on the 12ga, with lead loads.

Call me crazy, but I would (If I were buying my shells) start with the standard cheaper shells (i.e. Federal, Rio, etc) and see if I got the performance I was happy with. If I did not, then I might try something else like Apex, Pendleton etc.
I would also give William at Sumtoy a call and see if he can tell you what others are using with your gun/choke set up and how it is doing for them. He use to keep track of that sort of thing and was very helpful with this information...