[Morgeruat]

there are a few spells added by ToB (most notably the wild mage spells, and some lvl 9 ones)but these aren't available (without cheating) until ToB(IIRC) some may spawn in earlier, but not until near the end of the game.(the wild mage spells are available in SoA IF you play a wild mage, otherwise you'll never get to see them in practice)

Watchers keep is the only area that carries over from SoA to ToB, so you can stash EQ in there before ending SoA if you don't want to carry it on you the whole time. You can do Watchers Keep in SoA (I recommend lvl 1 before going to Saradush, as the items found there ("containers") are very useful), the other lvls can wait until you're more powerful, and can handle the dangers... the keep is basically considered a side quest in both games, something to do in your spare time, ie nalia's keep, trademeet, etc...