I just met a force sensitive NPC on a quest world who said that if you are force sensitive but not revealed, that you may notice you are slightly better at certain things than others..

Is this true and if so, what skills would this be applicable to?

That's just rp I think

It used to be so that certain skills were boosted. After the Force was changed slightly I was told that these bonuses would be smaller and hidden. However I am unsure if they are actually implemented or not.

Bonuses were removed completely.

Is being tested still operational?

You still need to be tested by an existing force user or by a force detector if you can buy/loot one, yes. NPCs cannot do that. Until you are tested you won't know if you are force sensitive.