In reply to Raphael.

Almost all block plugins will at least add a few kilobytes of load to the editor because they are written in JavaScript. As for the front end, it really depends on what the plugin itself does. Some don't add anything at all. Some add a little CSS. Others add some heavy JS.

The block editor in and of itself doesn't necessarily mean that plugins for it will impact performance one way or another. With that said, if developers stick to using standard core tools and block "supports," it is pretty easy to keep most one-off block plugins pretty lightweight.

But, again, it all depends on so many factors that it's impossible to make a general statement.