So here's my experience with stretchers bought on Amazon. Like you my balls were usually tight, even though I'm in my 50s. I've been trying to stay in an affordable price range. The best one I have so far is the "large" oval weight with the snap in ball bearing closure. I like that it can be put on or taken off without tools. It will occasionally fall off though. I put the small silicone ball rings on it to tighten it up a bit to stop that.
The two silicone rings were bought as a set of 6 or 7 and sold as ball stretchers. I find that they're too tight, and my balls turn colors immediately when I put them on. I use them as spacers on my larger weights, and sometimes as glans rings.
The "Small" oval is too small. Again, my balls turn colors immediately when putting it on, so I don't use it as a ball weight.
The round one with the C shaped slot. It could be great, but it is awful. If it was polished smooth in the channel where your sack goes, it would be great. Instead, they never finished it off, and the inside is rough, which makes it very uncomfortable to wear, and the roughness makes it difficult to put on or take off because it is like dragging your sack against sandpaper.
There's others on Amazon that are on my want list, but they're more expensive, so I've held off on buying them so far.
Even with my casual use of ball stretchers for about a year, I have noticeably better hang.