Yeah, I always try to give practical advise. Chances of checking staff being present in early morning is quite low, but still if you see any checking staff, don't act suspicious. Just be confident, ignore them and keep walking by taking advantage of crowd. You won't be caught.
Since you don't have heavy luggage, so if your flight is departing from T1, then better option is to take metro from NZM itself and then change to Magenta line via Yellow line. Take airport line from NDLS only if you're going to T3.