I don't know how I feel about the 'avoid retweeting' rule. Admittedly I don't have a huge platform, but retweeting for me has always been a way to introduce my audience to interesting new concepts or people to follow. Ultimately we're stronger as a network, not as individuals.
Also, I'm more likely to take advice on how to 'crush it on twitter' from someone who has achieved that already - this author has around 1700 followers which is fairly modest.
Fair point regarding retweeting. It's not necessarily bad. In fact, it allows other people to discover accounts you appreciate. However, it also makes it more difficult for someone visiting your profile to judge whether it's wort it to follow you.
Regarding your second point, I may just have 1700 followers, but I do have quite a lot of engagement: https://imgur.com/0oLirZP.
Additionally, followers don't really matter. Engagement does. You can have 1M followers, but if there is no one answering your tweets to put them in perspective, share ideas,... or liking or retweeting them, there is no point.
Also, I'm more likely to take advice on how to 'crush it on twitter' from someone who has achieved that already - this author has around 1700 followers which is fairly modest.