I have booked a few decent jobs off Thumbtack.
In general, very, very poor lead quality, sometimes bordering on the ridiculous, or possibly even BS.
IRRegardless if I plan to be active in such a service or not, if they are a legit major player, I always sign up and fully complete my profile.
It's mostly "pay to play" per lead and pretty cheap, but customers can also contact you direct if they choose, at least they used to be able to do so.
The less competitors in your area subscribing to the service, the better chance you may have.
They usually start you out with free credits if your a new subscriber, and a phone app to track leads and offers.
If you want to test the waters, the app will tell you if any competitors have submitted a bid on any lead that you have also been offered, and how many.
This might give you some insight into the number of competitors in your area.