Will the plant stay at a vegitative stage for how ever long I keep it at 18/6 and would it improve the more bud I will get in the finishing product if I leave it at 18/6 for a longer time
Veg time will last as long as you keep the lights on for longer then 18 hours a day. The flowering will happen during a 12/12 light schedule
yes longer veg time will grow a larger plant (if the conditions are right, specifically it has enough room for roots to grow) then yes you should yield more buds. But there are bunches of other factors that play into this, if you have a plant in a small pot and you let it veg for a extra month no it will not produce more it will just become root bound. expand with details on your question.