If you are using any Caching plugin then you should not cache the forums part. We use Cache Enabler, the very simple caching plugin. You can exclude forums, topics etc. of bbPress using the following regex.
caching
WordPress Simple caching with Nginx try_files
Now, we cache our sites in a simpler and better method. We use a wordpress plugin named Simple Cache. And we shall order Nginx server to serve the cached content bypassing the database query and PHP.
Accelerated Mobile Pages in WordPress
Accelerated Mobile Pages is a Google backed project for faster delivery of your website content to the mobile device users. Search engine shows AMP symbol.
FastCGI Caching with Nginx on VPS for WordPress
The best plugin for caching sites on Nginx server is to use no plugin at all. Nginx has built in caching module which is called FastCGI. It is the best performer on LEMP stack.