I also think there are different solutions for different amount. Different time preference as well. Is bitkey awesome for what it does? Its not great for me... Try as many as you can out.
I would avoid something like a RPI just because it has an entire OS as a threat surface. I would try a signing wallet but I also say. Play around with small amounts. There are a lot of ways to secure bitcoin and the more you have experience with the better
You don't install the raspberry pi OS to make a hardware wallet with the pi zero. If you use seedsigner, its just loading seed signers software... Same with pitrezor. There is no pi OS installed.
We see most of the times hardware wallet getting hacked because every company use cheap microcontroller and it's always available exploits because update not available from manufacturer or development slow or stop!