I think that if you want an edge for lifting/ no hangs then buying two rings is a waste when you can get single blocks with more edges/grip options for less money.
I have a pair and use one of them for no hangs. They're alright. Cord was easy enough to adjust so that I have my elbows and knees in the right position for a pickup. Since they're bulky (lots of excess wood) I don't find myself carrying one out to the crag to use as a warmup aid. This means that I have one that lives attached to the no hang weight setup, and one that collects dust. I should bring my own to the crag, but if I know my friend is bringing his: https://cruxforgedclimbing.com/products/unlevel-and-straight-no-hang-portable-trainer-claw-hammer I just end up using that instead. It's way less bulky, and has two edges in one "hole" so you can use the flat or unlevel by flipping the cord. Not affiliated, it's just nicer than the Metolius Wood Rock Rings II
I really like the unlevel edges for finger training too. A lot of people have started making them since I got mine so I’m not up on the products and won’t make a recommendation. For edges I like the Nug from Frictitious mostly because it’s stable (some shift a bit between reps based on where the cord is in relation to the edge you’re using), but honestly I’m sure most of the various products are completely interchangeable.
The cord is plain ole accessory cord. It’s bomber. The build quality is great, they just aren't the most versatile tool for lifting. It really only makes sense to buy them if you’re splitting the purchase with a friend and get a deal.