The timeline (one that Barry has not screwed with)
This is not an update
Okay, this is just going to establish some things about the characters. All the arrow verse characters exist on the same earth. Lex Luthor (from Smallville) created Doomsday and he is now in prison. Flashpoint never happened.
Team Flash
Barry, The Flash – After defeating Zoom. Barry gaining Zoom's speed, let's just say at this moment in time his speed is around Mach 10. Jesse and Dr. Wells form Earth-2 stayed. Barry never kissed Iris. Barry beat Zoom about 4 and a half months ago.
Wally and Jesse, Kid Flash and Jesse Quick – Both have speed force abilities. And both of their top speed is Mach 2.6
Caitlin – She is the same Caitlin form season 2, no powers.
Cisco, Vibe – Cisco is the one from season 3 of the Flash, he has full control over his powers.
Dr. Wells aka Harry – He is still a dick according to Cisco, but he has warmed up to Team Flash and they have warmed up to him. Cisco and Harry still have the father/son and love/hate relationship.
Joe – Still is a great detective and is still like a father to Barry
Iris – Well, she is going to be interesting to write, I'm going to let her events and actions later on in the story speak for themselves and leave it as a surprise for later.
Team Arrow
Oliver, Green Arrow – Oliver never assembled the new team and no Prometheus. He wears the suit from season 5 and has all the new and cool trick arrows. Laurel never died. Olicity never happened (I don't mind Felicity and Oliver as a couple, but I'd rather have Oliver with Laurel, like in the comics. I'm a huge DC comics fan.)Oliver is the mayor.
Laurel, Black Canary – She has the abilities of Earth 2 Laurel or Diana Drake, so she's a meta human, has been dating Oliver since right before the undertaking in season 1.
Roy, Arsenal – Never left, same suit form season 3 and the same badass. Never broke up with Thea because he never left, duh.
Thea, Speedy – She wears her suit form season 4 but its yellow, no more blood lust.
Diggle, Spartan – The Spartan from season 5 minus the whole prison thing, he never left the team.
Felicity, Overwatch – The exact same minus Olicity
The legends – Nothing is different about any of the legends.
Supergirl, the DEO, and Guardian
Kara, Supergirl – After everything that happened in season 2 minus Mon-El (Mon-El is my second favorite character in Supergirl, let's hope he comes back for season 3).
James – He will be hit pretty hard by losing Clark. He is the Guardian and Supergirl and the rest of the Heroes know.
Winn – The exact same from season 2
Alex –Director of the DEO by day, fights crime with the Justice League and her sister by night. May or may not be given some sort of powers or a specific ring that glows green that also is powered by a lantern. Other than that she is the same from season 2.
J'onn J'onzz, Martian Manhunter – Quit the DEO and joined the Justice League.
The Justice League
After Zoom, Damien Darhk, myriad, and the Daxamite invasion, the heroes of the world decided that they should never face these enemies alone. So they formed the Justice League. Oliver Queen was able to build The Watchtower before the Justice League was formed and before he lost his fortune, it now orbits the Earth. They all have access to Zeta tubes to get to other cities in an instant (That is from Young Justice, if you haven't watched it you should, it's really good) and they're able to use Zeta tubes to get to The Watchtower. The Justice League has been assembled for a few months.
The Trinity – The Trinity consist of The Flash, Supergirl, and The Green Arrow. They assembled the Justice League.
Members – The Justice League consists of Team Flash, Team Arrow, The Legends, The Martian Manhunter, Supergirl, and Superman.