You can use free panel, like the cyberpanel. Cyberpanel Enterprise comes with the free LiteSpeed Enterprise version, which is suitable for 2 GB RAM VPS.
Sure, but he has 5 domains and betting on Cyberpanel will add the cost of more than 1 domain.
I can also suggest ISPConfig, but do you have time to manage a vps? Does he have the knowledge? Another thing is that if it's a business, then I do not recommend CP for free.
But, given that the OP has 5 domains of little traffic, then there is no need to go with those hassles and the simple fact of using the hosting reseller is more than enough.