Samba is in dietpi-software:
This can dietpi-drive_manager do (or in dietpi-launcher) :
https://dietpi.com/forum/t/dietpi-drive-manager/560/1
That’s correct. It is a WiFi HotSpot.
This allows other wireless devices to connect and share the internet connection.
… but NOT to share your local network! (security reasons)
This is done via iptables rules: DietPi/dietpi/dietpi-software at master · Fourdee/DietPi · GitHub
You can change it manually, if you know what you are doing.
Correct. Your servers are behind NAT (MASQUERADE) for the HotSpot clients, as long as HotSpot is running or installed.
Example, same as for your LAN clients (and local server) are behind (P)NAT of your ISP router and they are not connectible from outside (internet) without a port forwarding rule.
Deinstall WiFi Hotspot via dietpi-software and you can connect via LAN.
Correct. A WiFi HotSpot without his own DHCP server make no sense.
Correct. This is caused by hostapd (service). You can change it manually, if you know what you are doing, but don’t expect too much.
CUPS?
No official support in dietpi-software, but web interface runs ONLY locally on http://localhost:631/admin and login is only possible for members of user group lpadmin.
To change this, have a look here:
But dietpi-software supports CloudPrint (CUPS print server, with support for Google cloud printing. Also includes a web interface for CUPS): (resolved) Execute code at startup automatically