(By the end of this explanation, you're going to need to add the "adult" tag)
The feeling is hard to explain, since you have weight and something you'd have to handle differently during bathroom breaks. The cage gets in the way of sitting down too fast, but with a snug fitting, it's quite comfy. The worst times was when I was sleeping and a testicle squeezed through the base ring, making it super painful and hard to wear, it had to be taken off immediately, but that issue was solved with a tighter ring.
I read in male fetish forums that the tube and base ring needs to so small, that it's a snug fit, to fully prevent erections. For cages, the erections can push the cage and tug the balls, causing said pain. I don't know if it's possible to actually stop an erection, though, so, I'm not trying that out, The best thing to prevent that type of pain is to focus on other things, keeping your mind clear of active thoughts.