Is there anywhere one can see the effects of spending Arcane Pool points for Magi weapoin enhancement? Arcane Accuracy (and the various elemental adds) toggle on and off but I don't know how to select them (to spend points).

If you go to the Character page, you'll see the effect of the Arcane Enhancement on your weapon if you mouse over the icon for your weapon at bottom left (you'll see for example Enhancement +1 or +Fire or whatever, as new bits in the weapon info). The effect of Arcane Accuracy you'll see if you hover over your Attack Bonus info just above and to the right of the weapon icon (or it might be below and to the right, not in game atm).

Generally speaking, with this game, the more you check in with all that info and the more you understand the effects various things have, the stacking rules, etc., the better of a handle you'll have on the gameplay.