can you do 2 of the same enchantments?
No, mostly.
You can find the enchantment for Resist Magic in random gear and then from the Shield of Solitude you can get a second
different Resist Magic enchantment.
Also, there's Fiery Soul Trap that can be added to a weapon along with Fire Damage.
Edit : According to the UESP.net list of enchantments, there are also two versions of Absorb Stamina and Absorb Magicka.