I will meet you sometime means at least one meeting. I will meet you sometimes mean several meetings are possible.

"Sometime" shows indefinite time or unstated time. So the sentence "I will meet you sometime" - means "I will meet you, but I am not sure when." You are busy, I am busy, we can meet in a year or so. "Sometimes" means occasionally, from time to time. "I will meet you sometimes" = "I will meet you soon". Say we work in the same building or our kids are going to the same kindergarten. Hope, it helps. ;)

No difference.