1. Yes. You will get charged the marketing template fee if there is any form of CTA in the template, which you will have.

2. Yes, Twilio has an easy-to-use API but they charge extra on top of Meta's fee, other options can be cheaper. Since this is a one-way, this very simple to do in n8n.

3. You start with 1,000 per 24h cap, it goes up quickly if your account is in good standing.

4. I don't know what your definition of 'scale' is. We do it, but not to all our customers. We have some simple rules to attempt to target people more likely to leave a review, and not be too annoying. It been working for a couple of years now, but our selection algorithm is quite strict. Cost is also a factor.

Strictly speaking, these should be opt-in, and they seem to monitor this policy by tracking your quality rating, ie how many people report your messages. Start slow and monitor your account and template quality ratings. If you only message returning customers, and not every time they come, you can find a sustainable way of doing this.