Here are links i've collected. I would speak to local counsel and have them review your process chart first. There is no 100% perfect source on this one.
BUT, in general
US = opt out (but I would use double opt in)
ROW = opt in or double opt in
DE = double opt in
Default - use double opt in.
blog.marketo.com/2015/08/marketo-data-tells-us-whats-the-truth-behind-the-two-biggest-email-volume-myths.html
Marketo Resource Center: marketo.com/b2b-marketing-resources/category/best-practices/email-deliverability
Benchmarks:
http://blog.hubspot.com/blog/tabid/6307/bid/33288/Answers-to-Your-Top-11-Questions-About-Email-Marketing-EmailSci.aspx
Marketo stuff?
https://www.senderscore.org/
https://en.wikipedia.org/wiki/Email_spam_legislation_by_country
blog.returnpath.com/9-essential-checks-for-email-law-compliance-in-any-country/
http://www.verticalresponse.com/blog/email-anti-spam-laws-around-the-world-infographic/
kb.mailchimp.com/accounts/compliance-tips/terms-of-use-and-anti-spam-requirements-for-campaigns