Maybe I misunderstood some things in your post (dunno if you were typing it in a hurry, looks like words r messed up in some way), but I'll try, so let's go:
1) For PvE, go back and read all majors thread in this section, as this matter was discussed many many times before, but keep in mind that a good healer work with timing = efficiency = easy for everybody > everybody'd be happy;
2) Dunno what you mean by "l2p", so I pass;
3) I guess by "requirem", you wanna mean "immortal", but stay cool, vorpal is fine if elemented right, and you can go till 95 and beyond if what you've got to focus is only PvE. For PvP, it'd be tremendously worse, so I dont reccomend that, unless you got nuts to, so your business, your minding;
4) Depends about the pace you'r willing to dedicate to game: if you r kinda hardcore player, then go with vorpal till 99 (in this case, I'd assume one is using all sort of xp boosts to lift up levels faster), but if your plan is about to be casual, then you can change that vorpal to seraph at 95+, so you'd be again cool to get your *ss to 99 with no hurry, 'cuz the set would be good for anything at PvE - again, your business, your minding;
5) PvP oriented healers go for CON, but PvE ones can focus on a more relaxated dyes setup, like WIT ones, combo of WIT/INT or even MEN dyes (but seriously, who healer goes for MEN since ever?);
6) Simple answer, pick w/e you want to. But if you wanna get advantages off your dual, then the choices would be restrict to: wynn, iss or tank, because of the class specific talisman (
https://l2wiki.com/Talismans) - you can check them by classes at the bottom of the page. In terms of gear wise, wynn would be the only choice (along with feoh). So wynn = pve solo, so you would need only a iss to box and xp away for good, or Iss, if you want to xp faster and get into every kind of instance, party etc.
Good Luck, I hope you dont get depressed fast by the class's beatdowns, tho. :)