Well you are putting your cock in a small cage, it’s not going to be super comfy, especially to begin with as you get used to having it there. The advice is that as long as you can get a finger under the ring it’s loose enough to be safe. The great thing with the CB-6000 is that you can start with the biggest rings and then work down to what size fits you long term best (and then get a metal cage with those dimensions).
We found it just took a few weeks of wearing it longer and longer and getting the right sizing before it really was comfy enough to wear a lot more. Don’t expect it all at once though.
As for erection after using it, opinion I read everywhere is that it has no long term effect. We find that it takes maybe a day or two for hubby’s cock to get completely back to normal after a longer period of wearing it but no other effects.
Metal devices are definitely more comfortable for longer term and they just look hotter too IMO. But start with a plastic one you can vary the size on and go from there.