I don't know if the RS500 is any different, but I have a set of WH-6800's, which look identical except the 6800's are branded with "Ultegra" on the rims. The hubs are different than 105, they use straight pull spokes but still have the same cup/cone setup that most Shimano hubs have. The 6800 was machine built with proprietary Shimano bladed spokes.
I bought those wheels back in 2016 as a replacement set for an old rim-brake bike. They were reasonably light, and less than $400. My experience with them was solid - I never had to true them and had zero issues for 5-6 years and many thousands of miles. I used them for road, but also as a backup CX training wheelset, running 33mm CX clinchers on them. I had a LBS service the hubs once, but beyond that I rode them on two different bikes without issue.
Eventually the rear hub bearings got a little crunchy and I tried replacing them myself, but the bearing race/channel that the balls sit in looks like it was damaged and they won't spin smoothly. I think it can probably be fixed, but I've never bothered to figure that out. The wheels are still hanging in my basement - I don't really have a use for them anymore as my rim-brake bike just sits on a trainer now.
I never ran these as tubless, only using tubed clinchers in them. I don't recall tires being difficult to install on them, but again... I never tried to install tubeless tires which typically fit a lot tighter than clinchers.