The counts sound ok. I recommend to get one or two spare boards just in case you missed something or stuff bursting in flames. For modern machines you probably want a 48V switching power supply. Should also work for the older stuff. 24V might also work. AC supplies definitely do not work without further electronics.
We do not recommend the RPi as a development machine. It just ain't fun with an IDE. Use some old PC or notebook. When it is all done you can switch to the PI.
You need proper ground and earth wiring. Otherwise this will be dangerous. The simplest way to get this right is a power filter board. It prevents a lot of dumb mistakes which would burn stuff or even might injur you. If in doubt get one.
Those sections should give a broad overview about the topics: http://docs.missionpinball.org/en/dev/hardware/voltages_and_power/index.html