I can add something here because I did some very similar to Matt’s case study.
I wanted to set something up to do some regular tweeting to promote content for my business, R for the Rest of Us. I use rtweet in a very similar way to Matt. The one piece I do in addition is to query a Google Sheet, from which I draw tweets and then post them. I did this using googlesheets4.
You can see the code I used here and the GH Action here.
See also canberramapbot (source) by Qiū Ruì, which uses londonmapbot’s underlying code. There’s also narrowbotR (source, blog post) by Matt Kerlogue, which builds greatly on the initial idea and incorporates calls to the Flickr API and embedding of geodata into the tweet.