1. Monk has an absolute insane amount of (almost bordering OP) amount of single target dps...If they have the uptime. Bard has the lowest single target potential, however it brings the most utility of any job in the game and you'll seldom want to raid without at least 1 Bard.
2. That's perfectly fine, do some leves, dungeons, fates, and logs for a day and you'll catch up on either.
3. Well SMN has the 2nd highest DPS potential...So if you want straight up deepz Monk is your style. Bard is for the player who wants to work in the shadows, basically carrying groups through wipe inducing mistakes by giving mana song/tp song to those who are rezz'd or the healers while Foes req provides an insane amount of dps to your casters. In addition your mobility makes you the "go-to" guy for special mechanics that give your role a lot of weight (Renaud's in T6, Homing Missiles in T8, etc)
4. Monk can be interchanged with Dragoon pretty easily (though MNK has higher single target but DRG brings better burst/increases BRD dps). However you'll almost never see an endgame raiding FC without a Bard in their static, so Bard wins soundly.