Ok this turned out to be a really long one so I hope you'll find it usefull:
Here we go...:
-Races do have passives and every race have a special racial ability --BUT-- unless you wanna be in the top 10 guilds in the world in PvE then they don't matter, it's a matter of a 0.5% to a 1% increase in output if --ALL-- the guild is taking the best race/class combo so unless you are THAT competitive then don't bother. Just pick the race that you are most interested in or the one that looks cooler.
-For realm you need to choose a faction before I can tell you what is the best server.
The ONLY difference between PvE and PvP realm is that in PvP realms ''Word PvP'' is enabled wile on on PvE realms it's not, but all other activities are enables in both type of realms the exact same way.
(e.g: if you are questing and you see some1 from the other faction on a PvP realm u can attack him but on PvE realms you can't.)
*After you choose what faction you wanna be, go to:
https://realmpop.com/eu.html and look for the type of realm you need and choose the one that have the most of your faction.
-I will be away for a wile after I make this post so I won't be able to give you a fast reply-
*Ok now for choosing a class what I am gonna do is tell you about the classes that can be healers and casters since you said you liked those and you choose what you think it's cooler or whatever appeals the most to you...
PS: there is healer classes I am not including cause they don't have a caster spec and I am not putting casters that don't have a healing spec ether...
Ok Healer/caster classes are : Priest , Shaman, Druid.
Priest:
Does priest stuff, praying, uses the holy light to support and heal there allies.
-they can do that with two specs, Holy (classic Healer, that uses spells reactivity to heal there allies) and Discipline (healer/caster hybrid that is more proactive healer then reactive).
ps: as of now the discipline spec is the hardest of the two.
-There dds (in WoW we call them DPS, damage per second), they turn into shadow priest where they loose there healing abilities to dmg there enemies with shadow magic to the break of insanity...
Shamans:
They use the elements of nature to aide them (water, earth, fire,wind, and lightning)
they have tree specs:
-Restoration is the healing spec where they use the element of water to healer there allies wounds.
-Elemental is the caster spec where they use the elements of fire and earth and lightning to damage there enemies.
-Enhancement is not a caster spec but a melee spec that the elements of fire and earth and lightning to enhance there weapons to damage there enemies
Druids:
They are shape-shifters that that shape-shift in to different animals to do different tasks.
there are the only class with four specs:
-Restoration: they don't have a special shape shift to do they stuff also you can turn in to a tree sometimes to heal with the power of nature.
-Balance: they are the caster spec, they shape-shift into a weird looking bird/bear/chicken/who knows what, (
http://1.bp.blogspot.com/-tjs67QyJzIQ/ToTWyXsgA-I/AAAAAAAAAVo/eQLSlXM3KPo/s1600/Screen+shot+2011-09-29+at+23.35.46.png) look at it and decide what it is...lol.
Anyway, they use a balance between the sun and the moons to do dmg to there enemies.
-Feral: is a melee dps spec where they turn in to a panther to attack there enemy in panther/ tiger style.
-Gardian: is the tank spec where they turn into a bear to protect there enemies.