Just play without worrying about the mechanics. Most of the truly gifted musicians and performers had no years and years of formal training.

They did what Diki said, they listened to others and then played what sounded good to them, not whether they placed the "correct" finger on a key, pad, string, fret whatever!!

The people who are technically brilliant, usually (to me anyway) are pretty boring in anything other than finger control and technique - there is usually none of "them" in a performance.

Thumb over or thumb under? Who cares, just play the damn keyboard