How many plugins is too many?

There is no magic number. What matters is what each one loads on every page and whether you still use it:

• Weight, not count - one heavy page builder can cost more than twenty small utilities.
• Site-wide loading is the problem - a plugin used on one page that adds scripts to all of them.
• Unused plugins are pure risk - they still need patching whether you use them or not.

Remove what you do not use, then measure. Deactivating is not removing.