So The Good Fight was a spinoff that had more ties (via character appearances) to the original show, although I still don't think you'd NEED to watch the original series to understand The Good Fight but it probably made it easier to understand certain things. Plus, it took place in the same town and in the same milieu (a law firm.)
Elsbeth is even less connected. She's in a new town and more a 'crime of the week' series compared to a 'case of the week' series like the original and the first spinoff. Elsbeth is similar to Colombo in that she's a lawyer embedded with the NYPD to observe them. She goes to crime scenes and figures out who did the crime.
There's a mention here and there of previous characters but nothing that would take away from the story they're telling.
That might change in the future but so far, the creators haven't indicated that they're interested in that.
