I prefer to open both doors at same time to be able to see all at once with easier access.

However if it's a small room then bypass doors are ok to get more clearance for furniture spacing.

Folding doors are annoying.

Good question.

Depends on how wide the wall is between door to enter & closet door. If all doors can open >90degree without door knobs hitting. I still prefer hinge doors.

If it's too close then sliding would do. It's the shuffling of back & forth to get what you need that drives me crazy.

If you are doing this to sell, either would work. Just avoid folding please.

Btw, I designed closets for over 10 years ;)