Hello @generosus,
Thank you for using our plugins and for reaching out to us.
Allow me to first jump on the easier questions:
“Also, can you point us towards your documentation explaining better your FBC feature? “
-> In general the File Based Caching preserves an HTML cache of your site pages. You can read more on the official KB page of the plugin:
(1) Is FBC compatible with other major caching plugins?
-> Yes, it is – however, it is always advisable to not use the case feature in several caching plugins simultaneously. For example, if you are using CSS Minification in one plugin, switch that feature off in the others. Same is true for the File Based Caching. If you have several plugins that offer this type of caching, choose one and disable it in the others;
(2) Is FBC compatible with Cloudflare and SGO Full Page Caching?
-> Yes, the File Based Caching is compatible with the Full Page Caching option in other plugins;
(3) Do we need to deactivate FBC before we clear our theme’s cache? (a good example is the Avada theme, which has its own caching function)
-> A general rule of thumb is to always go about clearing all your enabled caches (including the caching in your local browser) after you make changes to the content or appearance of your site which you want to show up immediately on the front end;
Now on the tough part in your post:
Since the release SGO V7.0, our website “feels” sluggish. Our website’s Clouflare caching level (% cached) has dropped and/or does not cache our website as fast as it used to.
We did many tests with the plugin and our observations are just the opposite of yours – file based caching resulted in even faster site loading than just the Dynamic Caching in our plugin alone. Of course, our tests were done in our hosting environment on SiteGround servers, where even the server level caching technologies are further optimized to work in line with the caching in the SiteGround Optimizer plugin, however you should not see any “sluggishness” on your site after the caches are once generated.
I would advise you to give that a test – preserve a backup of your site’s database, then disable all of the plugins bus the SiteGround Optimizer and then check if the site is still sluggish. Then you would want to enable the plugins in your site one by one to see if the sluggish behaviour might be caused by any of the other plugins.
Regards,
Plamen.M
SiteGround Tech Support Team