Add a 10K pullup if you see any erratic behavior.
E.g. pull-up resistor for momentary switches and flip-switches expected to be open most of the time and pull-down for the flip-switches expected to be closed most of the time? Or it does not matter? And external or internal or again it does not matter?
Interrupt pin? Puhleeze, that's a really, really bad idea. For many reasons.
Now how to connect them properly to be as nice to Arduino as possible (not to stress it unnecessarily)? It most probably folds down to being energy-efficient i.e. to draw as small current as possible in overall.
Unless you need to wake the processor from a sleep state.
Just connect and use the internal (30K to 50K pullups).Even the remote ones; they are not switching at high speeds, and unless your wire is really high resistance, the chip will read a low properly. Add a 10K pullup if you see any erratic behavior.