I'd argue that there are actually 3, but... Funny enough, my next little "series", after I finish writing about relays, will be focused around using Nostr practically. I don't intend to write about specific niches, but more broadly about stringing various applications & relays together to achieve a purpose, with a few exemplary pairings. I've been a bit busy & locked in my head lately, so progress has slowed. I'm glad you're seeing what I'm seeing though. That tells me it's not a terrible idea.
As far as helping to keep other things current, those are definitely tailored towards a "heard of nostr in a random YT video or tweet" type of audience. Broad and solid, I think, is important for that. I am no final authority on those, but it still feels appropriate to expose my logic, even if it only matters to 5 people 😜🤣