You'll never know unless you test. In marketing, it's all about testing.
There are a couple of benefits of Google Guaranteed/Local Services Ads.
You have no keywords to manage or ad copy to write.
You're taking one more spot of "digital real estate" on Google, in addition to your organic rankings, GMB, and text ads.
Your ads are automatically optimized for voice searches as well - over 20% of all Google searches come from voice search.
And finally, you only pay once you get a lead.
Think of these benefits and see if it's worthwhile for you to do them.
The point of this post is to help you understand some thing you potentially didn't know and to tell you that it's all about testing. What works for somebody else may not work for you and vice versa.