1. yes, you are correct, most of the features don't need to be implemented in code and having documented procedures would be sufficient (and that is pointed out in a number of places in the article). However, if you are not a small business or have a lot of users, the time needed to implement the features will be negligible compared to the amount of time needed for handling manual requests.
2. The "legitimate interest" legal basis is harder than it seems and many regulators warn against its overuse. Lawyers in my country are skeptical that regulators will accept legitimate interest in many cases, so "to be on the safe side" they recommend relying on consent. Again, as pointed out in the article, this is up to the legal team to decide.
3. The right to be forgotten is valid even under legitimate interest. Article 17(1)(c) is clear about that - whenever a user objects to their data being processed on the basis of legitimate interest. It is a bit hidden, as Article 17 refers to Article 21 which in turn refers to Article 6, but you can piece the whole scenario anyway.
4. About the best practices - agreed, they are not mandatory under the regulation (as pointed out in the article), but having them in place will demonstrate a higher level of compliance.