I was wondering what the standard length is for each part of a 3 note and 4 note chord. For example, if you have a 4 note chord that lasts for a whole note; do you split it exactly in half, playing the bottom two notes for two beats and then the top two for two beats or do you play the first half shorter and hold out the second half for the rest of the duration? I keep seeing people do it very different from each other in youtube videos so i was just wondering.
You definitely don't split the note value in half -- I've literally never heard of anyone doing that in 19 years of playing. In most cases, you hit the bottom two notes and let them ring, while moving on quickly to the upper two notes which are sustained. That is the default. The speed is usually as quickly as possible, but that may vary depending on stylistic considerations for the piece.
Composers may instruct you to play differently. You may see different note values for some of the notes than for others, in which case the notes with the longest values should be played last and sustained. (It's common for a composer to ask for only one note to be sustained, and I've occasionally seen music that calls for playing the upper notes first.) Also, composers sometimes ask for a rolled chord, which would mean hitting one note at a time, quickly, and sustaining each as long as possible while moving up the chord.