I am a long time mouse-on-tablet user, with Wacom Intuos3 6x8 tablet.
The mouse has many functional buttons and is very light since it has no battery. I recommend this despite the cost, especially if you are planning stylus work.
You would not use a stylus for Archicad.
Even though the dream is of the sketchy fluidity, the truth of navigating is pedantic repetitive exactitude - achieved only through using a mouse. You'll have the tablet in any event so find out for yourself, but avoid the carpool tunnel and stick to the mouse for drafting.
Stick to the mouse and get a house.
Use a stylus and prepare to buy less.
[complete with a better rhyme and get a prize]
Dwight Atkinson