I got a swift H axle which has been working well for me. I haven’t directly tested it back to back against an OTK H, but I can at least tell you it’s definitely in between an N and a HH at least. I did notice it seems to rust a little easier than my other OTK axles, but as long as you regularly clean it with wd40 you should be fine. I feel like for the money, it’s worth it.
I’d be really interested to hear what other people know about the swift MXC wheels vs the OTK ones. I’m thinking about getting some if they are a good replica but I haven’t seen any reviews out there.