Hi u/crmarks333, top 1% PvPer going to try and give you some useful information backed up by my own reasoning.

TL;DR
Top 2 small paddles only
A - left hand paddle
B - right hand paddle
Default Destiny button/stick layout

Before I start, I would like to note that I consider myself a top tier PvPer, 2.56 kd in trials (2.3 overall), top 200 in trials according to guardian gg, top 500 according to destiny tracker. (Both seasons)

The pro standard configuration is to have ONLY TWO paddles on your controller. Four paddles is too much of a cluster to effectively use. I leave the two top short paddles on my elite. (I use my middle fingers to click them)

The ONLY configuration change I made in Xbox Accessories app is: A button mapped to left hand paddle
B button mapped to right hand paddle
(This is actually the default elite controller layout anyway)

Default button/sticks layout in Destiny settings.

Here is the reasoning: As a top 1% PvPer, I want to keep my thumbs on the sticks while I am MOVING: walking/running/JUMPING/CROUCHING/SLIDING.

A lot of people here will say that you need to have X mapped to one of the paddles. Do not listen to them. Putting X on a paddle is a waste of your paddle. If you HAVE to be shooting the enemy while reviving a teammate, then as a team you all need to be more strategic. I'll elaborate, when reviving a teammate, ALWAYS think about WHERE YOU WILL BE STANDNING when you are reviving them. Always try to be behind cover when reviving a teammate, and if they being watched by a sniper, give the simple res-push. On the other end, if you are being shot and you know you will most likely die, you have to ACTIVELY be thinking about WHERE YOU WILL DIE IF YOU DIE. This mindset needs to always be occurring while you are playing trials. Try to always be in a "smart revive location" if you were to die, so that a teammate can easily revive you from behind cover.

I hope you find this information helpful, if you would like any more help, feel free to message me, and maybe we can even play some PvP together if you would like and I can give you some advice about how I use my elite during gameplay.

Thanks!