Is it appropriate to stop the website from IIS Manager? Including the default 433 for https and the SharePoint web services?
Yes , if you are not having any site collections under that web application running , then you can stop that web application from IIS Manager , which will reduce the resources usage by that web appplication in the farm.
and you should not stop SharePoint Web Services Webs site , its used to host all the WCF service applications , if you stop you'll face errors with 503
If you are talking about the Default web site in the IIS then yes Stop it. It is highly recommended in SharePoint that stop the default web site which cause trouble for SharePoint.
But if you have other web site in the IIS, you should check before stopping those. I am not sure which web site is configured on 433...
If you have Memory & CPU usage issue, then you should check which app pool is consuming more resources.
One thing, SharePoint performance depend upon couple of basic things.
- How much memory, CPU
- How many App Pools
- How much traffic is