W3tc surely is the best caching plugin for WordPress, in terms of features and provided options.
However, in many cases its benefits are zeroed by a too high server load caused by some features, that dramatically increases page generation time and causes throttling on shared hosting.
I searched for some information about this aspect and tried to put it together, but a clear, thorough guide is missing. This is what I discovered to date:
-minification is one of the most server heavy features,
-minification should be set to disk basic on shared hosting,
-database and object caching are often discouraged on shared hosting,
-page cache with advanced disk is suggested on shared hosting and should not give server load problems.
However, there are several aspects I would like to know, from the point of view of a shared hosting or other situations in which server performance is limited:
-how do garbage collection times affect server load? Roughly what garbage collection time should I set based on my traffic?
-how does cache preloading affect server load?
-among css, js and html caching, which are more server intensive? Are there safe settings that do not overload the server?
-browser cache should not affect server load, right?
-how do CDN settings affect server load?
I think that the plugin creator could give the best answers, even if with approximation.
Any other suggestion based on experience is welcome.