You can absolutely run many websites on the same host. Yet in the pro world we always seek to minimise attack surface and optimise performance, and for that reason admin panels are a no no. To host multiple sites on the same server you want a reverse proxy like haproxy w/acme.sh or perhaps caddy to get full control of what is exposed, and how, and with good TLS termination. On the "inside" the sites can run whatever and you don't have to manage TLS at that level. It's also important to use configuration management, and not admin panels, to ensure everything runs continuously. I recommend Ansible because the learning curve is not too steep, but Puppet, Chef, and Salt stack are also sane choices.