Legends won't be affected by what Barry does cause they are time travelers and immune to the changes . However everyone else is fair game it would be beyond stupid of the Arrow writers and Berlanti not to have this event effect the entire universe.
Well, they have done many "beyond stupid" things in the Berlantiverse, so be ready for more just in case.
The episode was not as good as the Season 1 finale, the writing was off like Season 2 was for the most part. First, Zoom wanted his lame Earth-2 minions to kill Barry; then, he just wanted to steal his speed to be faster, and finally, he wanted to destroy the Multiverse because... the writers could not come up with a better idea. At least, Eobard Thawne had clear and logical motivations.
It's funny how Zoom was so unbeatable all season, but when they needed to get him without Barry, suddenly and very conveniently team Flash could handle him, making Zoom even less impressive in the process. Bravo writers!
This whole time remnants gimmick is just lazy and nonsensical, your past self can die, but you will continue to live in the present just fine, yeah right... with this "logic", Berlanti & co could have another Zoom out there, so when they run out of ideas again, bring him back and tada!!
Then we have the time wraiths, very conveniently appearing just in time so Barry didn't have to kill Hunter (cop out!!). They could've intervened earlier to take care of Zoom, but it wasn't convenient of course, so they didn't. The show would be better off without these gimmicks.
On the ending, here we go again with Barry acting like an idiot. This would've made more sense last season when he had less experience, not now, specially after being in the Speed Force. Instead of moving forward, he repeats the same mistakes over and over. Yes, he lost his dad, but he still has Joe, Iris, Wally, friends, people that love him, a whole city that loves him, but no, is not enough, undoing the progress he made in the Speed Force.
Regarding the consequences of Barry saving Nora:
Logically, it should change the entire DCTVU. Arrow should be different in Season 5, Legends of Tomorrow... For example, Barry would never go to Starling City like he did on Arrow 2x08 The Scientist, him and Oliver would never meet and become friends.
And if they do a Flashpoint adaptation, is not going to be as epic, Arrow is not going to be without Oliver for several episodes, Legends has already set its own story for Season 2, they're not going to undo it. I won't be surprised if Barry realizes that he doesn't want the life he's created by saving Nora and this gets undone in the Season 3 premiere, and everything snaps back into place, except for a change or two. It wouldn't be outside the realm of possibility, The Flash's time travel barely has rules, it has altered its timeline without any consequences to other shows.
I think they should do a Crisis, something really epic affecting the Multiverse and changing it for good, creating a new reality, a new Earth-1, where Superman, Supergirl, the Martian Manhunter, but also Batman, Wonder Woman, Green Lantern, the whole DCU exists. This stupid policy of only having one version of these characters is unnecessary, they should get rid of it, Geoff Johns has more power now, but maybe not enough to make it happen, time will tell.