I think Lennox would either be a water bender or a firebender. Water bender because of the amount of precision and control you need to control water and also the flow. firebender cause Lennox looks like he's from fire nation and I want him to be an arsonist, causing mischief.
Yusrif would definitely be an earthbender, using earth bending to troll people like making them trip on purpose or throwing rocks on their faces, he would be the evil melon lord.
Lennox would mess with yusrif by throwing water at his face to wake him up or making him wet on purpose and Yusrif would mess with Lennox by making him trip everywhere.