Child Theme configurator seems to run once, create a child theme, and then step out of the way. I’d use it, disable and even delete it if I didn’t think I’d need it anytime soon. I do like that plugin.

The Broken Link Checker can be a resource hog as it runs out of the box set for something like 72 hours for each traverse. I usually throttle it back to 480 hours after it has done its job a couple times. You can also disable it and re-enable it occasionally but the sites I have it on need it to run continuously as the content can be right dynamic.

This website can help you find bottlenecks if you’ll run it once in a while over your website. https://tools.pingdom.com/.

I always figure if you need more horsepower then ‘buy it’. Hardware in the form of server upgrades are cheap enough. Don’t overburden your web server with extraneous tasks like email, webmail, cron, DNS, etc. Let it be a web server first.

You might look at CloudFlare for an approximately 20% performance boost after you solve any speed issues. I love CloudFlare (especially their DNS service) but it can amplify 500 errors.