I have level 94 bard/cleric, currently soloing on level 96/97 mobs when there is no guild/union party.
Can it solo well? Yes. After level 40 when you get Recovery Division (cleric sub) you finish grinding with more pots than you started with.
What Sub? If you want to play bard as your main, I suggest cleric sub. All others subs will become your main, example wizard/bard.
Is it cool? Depends on what you like. I love being a support character but still able to survive on my own. I don't care about big damage numbers. I don't care about seeing my name because of killing an unique (very rare to see that as a Bard).
Can it kill lots of people when in a group or maybe event? Solo pvp, you die frequently. Group pvp, you make everyone kill faster, survive longer and often kill steal your party mates.
What skills to take? See
viewtopic.php?f=5&t=88001Pure Int or hybrid? Pure Int because your damage is purely magic based. Cleric sub will keep you alive so extra Str doesn't help you.
I can survive and kill 3 or 4 mobs my own level almost as quickly as a wizard. I can survive and kill 2 or 3 mobs a couple levels higher than me.
I can outkill same level Chinese nukers. Giants are not a problem once you have Recovery Division (level 40 cleric) and Bless.