If you want to use Add-ons, you need to fully flash your Pi, yes that’s correct.
Trust me (and likely most others in this topic), when they say you won’t need your GPIOs on the Pi later on. If you want to run your home automation stress free and reliable, you will want to install HA-OS. All other things will run via HA in the future, and there are loads of possibilties to use other things like ESP based devices to get your DIY style home automation.
Most people here, that started with other installation methods are now running HA-OS, because it is the most reliable way to run HA.
The differences are not that much (depending on perspective) to Pi-OS, but with HA-OS there is somebody behind it, that takes care of all the nasty little pitholes you can fall in. Let me give you an example from a few weeks ago:
Pybluez
is a package for Linux (incl. Pi-OS), that is no longer maintained. This wasn’t much of a problem, as long as it worked. But times move on, and requirements are getting higher, so with a new python version, pybluez
isn’t compatible anymore… For HA-OS there seem to be a solution, but who is taking care of all others? There is no way, that HA takes up the unmaintained repo for pybluez
, other maintainers don’t seem to be on the horizon, so pybluez
is dead. And now? That’s just one example why HA-OS is better than Pi-OS and core or container (or supervised).
That being said, let me ask you a question. What do you have in mind, that you’d need the GPIOs for? What is it, that you think about doing? I can practically guarantee you, there are at least two other ways doing it with HA without the need for GPIOs on your Pi.
TL;DR I know, it’s much to ask, but trust us - do the install with HA-OS and ask if you have any questions. I can guarantee you, in about six months, you can come back to this topic and will tell us all, that it was the right decision!