Confused about Core Updates and Desktop Optimization

I am slightly confused about whether or not I need Yanfly's Core Updates and Desktop Optimization plugin. I did a fresh install of RPG Maker MV on the 1.6.1 update and my current project was started on that update but I am aim for my game to primarily desktop PC based more than mobile so should I use this plugin? Is it safe to use even if I am on 1.6.1? I see I can turn off the updates in the plugin's parameters and just use the desktop optimization. Insight into this would be greatly appreciated, thanks.

no plugin is ever needed automatically.
You install plugins if you need their functions, otherwise you don't install them.

That is because the higher the number of plugins, the higher the chance that some are incompatible to each other.

Can a high number of (compatible) plugins cause lag?

Lag can have many causes, because it literally happens if the computer does not have enough processing power or memory to handle everything it is tasked to do.
So it all depends on what the plugins do - a single badly programmed plugin with massive tasks can lag a computer than could handle hundreds of better programmed plugins with minor tasks only.

Increasing the number of plugins increases the chance of getting problems, but it all depends on the individual combinations.