I'll give my opinions on this from what I've experienced talking to people who've owned chastity belts.
- I think a closed one would be better as having open which is more open could cause pinching around the head which could make it harder for long term wear.
- It'll be very hard to have an ruined orgasm through chastity and it really depends on which toys you have vs which device you go with.
- This depends on the belt, some have large holes and some may have no hole at all. Some even come with urethral inserts to aid with peeing (and a bit of teasing).
- Almost every device is lockable in some capacity. Some use padlocks and some come with built in locks.
- Plastic is light and from what I've heard more comfortable but steel is more hygienic especially when it comes to peeing and stuff.
- With a cage you might notice the weight of it, another idea is to get a full belt which kinda eliminates the weight issue but some with their own (mainly size and cost).
- Most cage designs will cause a bulge meaning that you can't wear them under tight trousers without them being obvious. Some belts are design to stop this but you also have the problem of having the full belt and the cost.