Varnish is a popular reverse proxy which is used to accelerate page loading by caching copies as static HTML. This increases performance, but works on a higher level than the HTTP protocol. To use SSL with Varnish you'll need to offload SSL traffic to another web server. Most commonly it is Nginx, but H2O currently the most advanced implementation of the HTTP/2 protocol.
You can transfer content automatically from WordPress to Drupal to eZ Publish (nowadays eZ Platform). To help you get started with your automatic content migrations from WordPress to eZ Platform or Drupal, you'll want to hire skilled partners to do this for you.