Higher-level (360+) Enchantments are available for rings, however it is only a self-enchant and is non-transferable (you can't use the enchant on an [Enchanting Vellum]. Once a ring is enchanted, it will become soulbound to the enchanter if it isn't already.
Some NPCs wear rings on their ear(s) and/or nose.
You cannot equip two of the same name/type rings.
Exceptions to this are rings that can be purchased with Honor Points at different levels, such as Protector's Band, which can be double-equipped provided that they are different levels, e.g., [Protector's Band] at level 38 and [Protector's Band] at level 28.