Why they are free
A gated tool does not get linked to, and links are the point. It is also a reasonable way to be useful to someone who is not ready to buy anything.
Which to start with
If you hand anything over in person or have a premises, the QR code first — the highest-return thing most local businesses can do about reviews, for the price of printing. If everything happens by email, the review link and the request templates together.
If the problem is replying rather than collecting, the response generator removes the blank page and leaves the judgement with you.
And then
Collecting reviews is half of it. Showing them where buyers decide is the other half, and that is what the widget does.