Don't add unnecessary weight... so only box the spoilers if it makes sense to strengthen the wing with the box structure or if you expect airflow to want to inflate the wing if its not boxed.
A secondary reason some people box in the spoilers is the tendency of the covering to pull the frame around the spoilers into little bows between ribs, but wider strips around the spoiler bay does more for less weight.
About half the deflection angle for flying stab vs fixed + movable elevator. You can add more throw if you feel the need for aerobatics, but +/- 20 deg from neutral will be plenty to fly.
You may desire some expo to tame it near neutral.
Note that your spoilers being well out in the span can mean yaw if they don't deploy evenly. You can make use of that by programming a mix with rudder or aileron.