I disagree somewhat strongly with your point #1, or at least I have a different framing for it. Don't bother focusing on depth in a very small number of programming languages or technology stacks. There isn't enough depth there to make that worthwhile. Programming languages are fundamentally similar with very few different paradigms, all of which can be learned and then applied appropriately to new languages. You can learn the more interesting or fiddly bits of any specific language you're working in as needed.

But depth of domain might be worthwhile. That is: "I work on distributed data storage systems", or "I work on data analysis systems in the energy industry", or "I work on self-driving sensor data analysis", etc. Maybe I'm wrong about this, it's certainly not the way I've done things, but it is the kind of deep expertise that I'm often envious of.