[Pikami]

I'd say updating everything is a must, including your Pi.

Of course, but you're not going to be updating your stuff every day...

In a typical setting, I'd imagine you don't have to for your browser either. That said, many people use both as Pihole only targets DNS.

Yeah and I can imagine that most people don't even update their piholes after setting them up, I guess it isn't the end of the world if they don't expose it to the internet, but may still be a security risk.