Need some help understanding some things and getting back into the game

So the last time I played this game was when it released. I quit just before season 1 dropped due to IRL stuff, coupled with the fact that my gaming pc pretty much died.

So now I'm back. And boi… The game feels so different from what I remember. I need some help here…

Of course, the map is different. Did they change it from Kings Canyon or was there some kind of event that reformed the terrain?

Octane? Is he good? I think I might not like him that much based on quickly reading through his abilites but the launch pad seems fun. Is it viable to use? Is he worth the time and effort to learn?

Wattson doesn't seem like a character that would fit in my playstyle, how useful is her "gate"?

I might main Revenant, just because I've always loved evil characters and his abilities seem pretty nice + he looks pretty badass. Again, is he viable?

Now to the weapons. Is the "L-STAR" something I should be using? It feels pretty slow and I'm not sure if the damage is the greatest.

Sentinel feels… unnecessary? I like the Longbow better.

Overall I need some help understanding the currrent meta and what loadouts and legends are considered viable etc… Soo anyone willing to explain some of these things?

Thanks in advance. Excited to start playing again.