Anyone also know which charm to use? Are they all the same strength or is a certain element the best ?
NR1 gave you the correct answer that all items have the same AVG damage ... excluding Heavy Weapons.
Ice & Focus charms have the best "Consistency" to either damage or heal out of all the charms.
Lightning & Wild charms have the highest "Inconsistency" to either damage or heal out of all charms.
... However, it comes down to personal preference. I would personally use Lightning or Wild Heal charms, that is because they can be used by a Headhunter, even if they only start with a Base Intelligence of 5 and are considered more for Melee build and not Caster/Heal... I like being the odd duck okay.

Up to you and your play style... group or solo.