Locker stacks are cool... but a word of caution
There are several stacks out there that hide things from your preview and published page. I have one called Locker but there are many others out there.
How do every single one of these stacks work?
They block content from ever getting loading into the HTML. However, they cannot stop things from loading CSS and JS.
Why does this matter?
Many people place things inside a Locker (sometimes even hidden inside a partial) that contain tons of stacks. Locker will definitely hide everything from the HTML. However all of those stacks still output CSS and JS to your page. Therefore, it does add some weight to your page. An even worse side effect is that some JS will run on the page and expect to find certain elements in the HTML. When that does not exist, it could cause JS errors on the page and break your entire page. This is not true of every stack, but it is possible.
So use responsibly
These stacks are mostly meant for you to store notes in Edit Mode (my Locker stack will add zero weight to your page with this use) and maybe hide some simple things. Or temporarily hide some stuff for testing purposes. However, do not over use them and store tons of stacks inside them for long periods of time.
Now go forth and make your websites great!