Best way to manage browser extensions without slowing down Firefox?

Disable extensions you don't actively use instead of uninstalling them, so you can turn them back on quickly if needed, and stick to lightweight ones like ad blockers rather than memory hogs. Also check your extensions' permissions regularly - some grab way more resources than they should, and disabling the ones that auto-run in the background makes a huge difference!

The trap people fall into is installing a bunch of extensions and then just... leaving them all running in the background. What actually helps is checking your about:performance page in Firefox to see which ones are eating resources - sometimes a popular extension turns out to be way worse than you'd expect. Beyond the usual advice of cutting down to what you genuinely use, it's worth looking at whether any extension has an option to reduce its activity (like ad blockers that can skip certain sites, or tab managers that only activate on demand). A lot of people don't realize those settings exist because they're buried in preferences.