Other than the bonuses, or as a backup for close quarter fights, there is no particular benefit to equipping a sword and shield for a mage.
I wish to say something about this :
playing a Priest I need many Mana. In the first place I only used a bow or 2-handed sword, but since I love trading and see nice shields with a good bonus to Spirit (and/or Vitality!), I buy that shield. Further on in the game you must fight against 'Laiken' and his Sword gives +2 to Summon Mastery, a Priest Skill ! So since then I use that 1-handed Sword and yet the best shield I can find or buy ! And if I see/find a better one (with a higher bonus to
Spirit/Vitality or more empty charm slots - to put Intelligence charms in them for a faster Mana regeneration(!), I change to that shield and sell the lower one .
But you can concentrate also on Spirit boosts on all other equipment so a shield isn't that important anymore. Probably in my next playthrough I wish to play a Mage Priest without shield & sword and only take a bow OR 2-handed sword, because I love that more than sword + shield .
You should be able to see the formula in your inventory. There is no way to check the ones you have other than by talking to an alchemist (I kept a written list handy when I played, to keep track of the potion and enchantment formula I had).
I do the same : making a list of all my formula's (for potions & enchantments) & for all creature bodyparts + many more I write down while playing
