My (layman) path to growth suggestion would be to start with nr 2 using the mechanisms you describe in nr 3 internally ($1M to $3M ARR), and then slowly expand to comparable verticals until you have about $10M to $20M ARR. After that you can start productizing the internal tools you built to the public and become a platform.

(Mostly written from a GTM perspective, and including the obligatory disclaimer thatI'm still way below $1M ARR myself, so take this with a grain of salt...)