I can shed some light on the hardware part. Since mentioned that you wanted to build an NAS with RPi 5, I strongly advice you to go with the certified power adapter along with active cooler. Rpi 5 usb ports can handle 1.6A of power to downstream USB peripherals when connected to a power supply capable of 5A at +5V (25W). When connected to any other compatible power supply, the Raspberry Pi 5 restricts downstream USB devices to 600mA of power.Wanted to build a NAS & want it to be accessible from anywhere.
for the experimentation i've a desktop descent configuration but it'll be only for experimentation if it works i'll go for a Pi nas
Components will be
Pi 5 8gb
Sata hat
Sd card 128gb
and may be 2.5' ssd or hdd
but the main issue with this is i don't know which OS to use according to my research OMV fits according to my need but still don't know how can i be accessing it from anywhere in the world will be needed some guidance on how can i make my nas routable.
Also, if need to add more drives or higher capacity or power hungry drives then you need to consider buying one of these Active Powered USB Hub