Is this also true for popups? I recall reading somewhere that popups inside reusable elements aren’t loaded into the DOM until they’re triggered.
I could be wrong, but if that’s actually the case, it would be a game changer for performance.
Plugins become an issue when either:
- the code is bad or unoptimized
- it has large chunks of shared code (code that loads regardless of element)
- it’s calling and loading large or tons of libraries (which is the issue with the material icons plugin)
- a CDN the plugin is requesting goes rogue
- Or a mix of any.
Size of the code isn’t an issue, but some plugins have bad code. I know cause some of my plugins are still unoptimized 
Other than that, it’s pretty safe to install and use plugins. I will usually look at the plugin code where I can before installing. For paid plugins I’ll trial it and check the code after the fact.
There are popular plugins with scary bad code. Look up a popular “copy to clipboard” plugin, it’s using weird deprecated methods and calls a 3rd party library that isn’t even used.
I can use a really long list of clean client side plugins
I can give one that is great for SPA; Data Jedi