So NEMA17’s should be fine if your machine is not too heavy, something around 50-80 oz/in should be OK. Vortec RC uses NEMA17 on their kit. www.vortex-rc.com/product/4-axis-diy-hot-wire-cnc-for-rc-hobbyists-aeromodellers-and-designers/
FoamLinx offer several machines but these are not really aimed at hobbyist, costing several thousand dollars. However, we can see they are using NEMA23 rated at 220oz/in on their small machine.
My current CNC foam cutter uses NEMA23 motor 175oz/in rated at 2.8 Amps. The moving parts on my build weigh a little over 11KG or 25 lbs, so it’s a bit on the heavy side. It’s made from 3/4″ (18mm) High-Density FIbreBoad(HDF) which is very strong and stable but quite heavy. So I decided to use the bigger stepper motors with the recommended 24 Volt power supply.
My updated design for 2019 which will use 12mm MDF and features several changes and improvements. It reduces weight considerably and allows the use of NEMA17 steppers. Keep checking back for the updated design should be out soon.