Just my personal opinion but.....
1. You don't show any celebration before the final 9 goes down. Filler whooping after he pocketed the 8 was a little uncool in my book. He's young, tho, and I am sure I did plenty of classless things at that age.
2. You shake the opponent's hand very first thing after that ball goes down. They are feeling crushing disappointment at this moment, and don't need to be "held hostage" waiting to shake hands whilst all manner of warbling, fist pumping, and breakdancing are going on. The last place they want to be is beside that table.
3. The very limit of what I would find "okay" as far as celebrating before shaking opponent's hand is something like when Archer laid his head and forearms on the table after a tough final match that ne won hill hill. This communicates how relieved he is to have the pressure gone, and is not rubbing in the victory for the loser.