For now I am only using the Object Cache with Dragonfly across multiple websites using different cache keys, which is working great. Full page caching by Apache/Redis is not supported. I believe there is an Apache module but it has to be compiled into Apache first?
Any cache plugin that writes to .htaccess (for Apache) and then generates .html files is better than one that connects to PHP or any other in-between to serve data. Here is an example when the page is fully cached:
Apache -> show cache page
Apache -> PHP communication -> Redis communication -> show cached page
Right now I am using WP Fastest Cache as this stores static .html files of the pages and serves them via .htaccess.
Once NGINX comes, for me this would be the preferred solution because reading from Redis memory is significantly faster than disk. In that scenario, even though NGINX must communicate with Redis, I would imagine the time spent doing that is negligible (although I am not 100% sure), i.e. NGINX -> Redis communication -> Serve cached page
I did try the Docket Cache WordPress plugin as well, but on my larger website I found that it was causing a significant slowdown and I am unsure why. Once I disabled the plugin, the website ran fast again. This plugin is a very good tool though for smaller websites as the speed was comparable to Redis.