Well basically I came to an idea that what is the point of enchanting weapons with supposely higher soul gems such as Grand Sould Gems or Black Soul Gems, when we can combine other "lower" soul gems and at the end result the item is still crafted...... Well besides the point that the Grand and the Black, they can capture souls.

Oh and where can I find "paralysis" enchantment? Or an item that has that enchantment..

What? You can not combine soul gems. Bigger gems give more charges for enchanting and recharging. The also increase the effect of the enchantment.

Higher soul gems hold better souls. Better souls = better enchants.

You can combine to charge but when your at the Arcane Enchanter you only have the option to select on gem. If you select anything below a black and grand soul gem your enchantment will be considerably lower. If your combining them to make enchantments then your the only one doing that.