So I think the tracking forb tech is an extension of the technology we’ve seen in the films that can detect life signs on ships or escape pods, except they are synchronized with the biosignature of an individual (I’m guessing with the use of DNA samples). I’ve seen people complain about it making bounty hunting too convenient, but I think you still have to at least be on the same planet as your target to be able to track them hotter-colder style. It’s a big galaxy, so laying low on a backwater world is probably a good idea unless you stir up some trouble or someone spots you in a cantina or something (which is probably how they were found in episode 4).
I’ve noticed a quite a few comments regarding the last two episodes being “filler episodes” with little purpose. I think it says more about how the landscape of television has changed in the past twenty years. Shows have become more focused on an overarching narrative rather than being episodic, and I think that has led people to feel like it is a waste of time if the plot isn’t being moved forward in a very direct way. I like the idea that show could just be about Mando trying to survive in this lawless galaxy (and being a single dad).
EDIT: I think the character at the end is just Mando, and went back for her for some reason.