Here I'll explain a few things about these builds.

First of all, why TP?

Here's the thing, Yunara has a very powerful clear and a very good potential to split push, as an ADC your job is to always help your team in fights, so with TP in hand, you can easily stay with your team, and if you need to, you can also split push (sometimes you'll need to be the one doing it, I would not encourage you if you were playing another champion, but with Yunara it is safe to do it, UNLESS you're going for the AP or Crit build, then DON'T).

About the first build:

I tested many builds and this one is the strongest one in my opinion because it takes advantage of Yunara's abilities while giving you sustain to solo carry. I'm gonna be honest, most of the games you will win before you finish this build, after Yun Tal you are already deleting almost everyone, the remaining items will only provide you sustain to endure long teamfights.

AP Build:

This build is for fun, you're going to one shot people, it has a lot of burst damage, you can use it in competitive games, it is strong, but not stronger than the first one so I don't recommend switching to this one, unless you're playing Yunara Mid, then it's ok.

Now the AOE Build:

This one is a pretty fun one with a lot of potential to dominate teamfights, clear waves, and take down turrets. The secret here is to focus on teamfights, when everyone is together, just start AA and you'll see everyone getting deleted at the same time, but this build relies fully on your positioning, so pay attention to that, stay behind your team. And this is the perfect build to split push, if you need to do that, go Hullbreaker after Hydra (don't go BotRK) and take advantage of your TP. Black Cleaver can be a better option instead of Terminus depending on the matchup.