The PBS wheelset is of good quality and I'd recommend them having built my own set of Grails with Bitex hubs. I believe they're built by Sta-Tru in Santa Ana, CA. I'm not sure of the hubs manufacturing origins, but I'd put their quality around that of the Bitex hubs I'm using on mine - Similar weight, Enduro bearings, Shimano/SRAM XD freehub body, serviceable, 4 pawls, modular to any axle format.
https://speedtunedwheels.com/product/super-6-2-0-hub/
Besides that, I believe they use DT comp spokes. All their wheels have always come in true and evenly tensioned. Again, would recommend, especially as they're probably going for around $400 now.
Edit: To answer one of your original questions, you would not use the Stan's endcaps. Rather, you'd have to purchase them from the above link I provided.