Hassio on RPi - how many addons?

How many addons on Hassio RPi 3b+ can handle?

I plan to install HA, Pihole, node red.

Depends on how much processing power each container uses but a 3b+ should be able to handle it. You’ll know when you need to upgrade to better hardware.

Find string
measure string
take measurement of string and multiply by pi
divide by sqrt(e)
That is your answer.