I've tried all of the panels over the years.
And so far CWP fits he best. But I'm also old, and use to use RedHat in the early 2000's when it was free, before they went paid and release their 1st version of Fedora.
Then maybe look at ISPConfig (Donation Based)
As it also has an auto install script (
https://www.howtoforge.com/ispconfig-autoinstall-debian-ubuntu/)
I would use Debian (Release) over unbutu (Beta).
Updates are very slow, it has it's own proprietary billing system (
https://www.ispconfig.org/add-ons/billing-module/), that is 59 Euros.
That being said, WHMCS and CPW is a great combo, but I do understand the minimum for WHMCS is $18.95 to $44.95/Month.
Depends on what fits your needs the best, not for just now, but you have to look down the road.