If I am using a hosting provider like Bluehost, or a2, should I also use cPanel ? cPanel is an admin interface and what looks like a handy utility for administering my server. Are there advantages and disadvantages to using cPanel?
I've certainly found cPanel very useful to do lots of things and easier that using ssh access (some hosting providers might not provide that). I have found it does everything I need that can't be done in the CiviCRM UI. My hosting provider (Siteground) has moved away from it to its own control panel which covers all the same functionality and has some better functionality, but there was nothing wrong with cPanel. Of course it also depends on the functions provided through cPanel as its a toolkit and they might leave bits out.
so my suggestion would be to go ahead and use it. As much as software can make things less secure, in this instance the cpanel is probably setup to auto update so its not something your managing and its probably installed on the server anyway so whether you use it or not, its going to be present.
From the other side of security, the more that the panel can do for you, in terms of checking, configuring and recommending, the better your security is likely to be. The modern panels have all sorts of plugins which will enhance and not detract your experience.
Think of the panel like any CMS such as Drupal or Wordpress. Yes, you could create a website without them but they provide a hell of a lot out of the box and keep getting updated. Hosting panels are similar, they offer you a bunch of functionality that will make your life a lot easier.
It's a tradeoff - it does a whole bunch of stuff that you don't need and some types of custom configurations can be difficult or get overwritten, but it does make some tasks easier, e.g. SSL certificate autorenewals, split php versions for different sites, creating mysql databases, etc...
And I'm not saying cpanel is insecure but just as a general comment about any software the more stuff you have running the more surface there is for attacks. It does let you turn off some things.
It is true that the more stuff you are running then potentially there are more attack vectors. If you are not comfortable doing all the low level config on the server or are not an expert then using something like cPanel or Plesk will give you more confidence. Additional extensions are available to do things like security checks which can be invaluable. It's always a trade of though - if you want to be able to do deep level tweaks and config and want to squeeze the max performance out of the server then go without.