1) Every class will look different. theres also a glamour system so you can actually choose how you want your gear to look like.

2) normal, theres only voice acting in certain cutscene

3) Healers and tanks have easier queue when finding party, so i'd recommend them if you're trying to level ur 1st character

4) If you're going DPS, just choose whichever DPS u want to play.

5) you can get to level all different jobs in 1 single character and stats added are unique to the class itself. So what you added to your stat while levelling your healer would not affect the other classes you play. Also, racial stat difference is too little to affect much, so just choose whichever race appeals the most to you