Newbie using docker, use cases where docker is suitable

I have multiple websites on a single VPS with admin panel (VestaCP), most of the website is simple and use wordpress.

Now I’m investigating dockers and I want to know if docker is suitable for host multiple website on a single VPS?

And how should I manage that I have multiple dockers for each website (php / apache, mysql, email), or should I have single docker for each service, and then have multiple databases under a single mysql docker, have multiple websites under a single apache / php docker?
I’m a little bit confused, at the moment using vestaCP is very easy to add a new website, if I implemented dockers probably I will complicate the process.