I was wondering if its possible to set up BTT so that a single finger double tap on the trackpad effects a left-click?
No, BTT doesn't override the system single finger tap. Whats your use case for this? Are you aware of the tap to click feature in System Preferences => Trackpad?
I have an older MacBook Pro (non Force Touch) where you can't adjust the finger pressure required to register a tap. I find that it's too easy to accidentally register a tap while using the trackpad.