Tumbling opportunist

[The Total Package]

As a halfling if I use this feat against a larger opponent, would I suffer a penalty for trying to Trip a larger enemy if I used Acrobatics?

https://2e.aonprd.com/Feats.aspx?ID=6245

[YuriP]

Yes. This ability doesn't change how Trip size restriction works even when used with acrobatics.

You still needs to take Titan Wrestler to Trip a Large creature. In general it's hard for small creatures to Trip or Grab bigger creatures.

[The Total Package]

Would Titan wrestler even work since it says Titan Wrestler works only for Athletics?

[NorrKnekten]

Titan Wrestler says nothing about Athletics except for needing a certain proficiency to pick the feat, and improving at Legendary athletics.

Titan Wrestler wrote:

You can attempt to Disarm, Grapple, Reposition, Shove, or Trip creatures up to two sizes larger than you, or up to three sizes larger than you if you’re legendary in Athletics.

So yeah, Titan Wrestler applies regardless of skill used for the roll.

[YuriP]

The only restriction of Titan Wrestler is that you have to be trained to get it and it will only increase to 3 larger sizes than you if you are legendary with athletics but it doesn't prevent to get its benefits with different skill rolls as well pointed by NorrKnekten.