IMO, it isnt a great idea to try to add new mass and go straight to a cut. your body needs time to hold onto the new muscle you've gained. when you cut calories, the first thing your body will want to do is drop the new muscle. also, 6 wks, is not much time to cut. you want to take your time cutting and slowly reduce the carbs and fats. i would suggest 16 wks. all you're really going to do in 6 wks, is lose a little fat, not enough to look "cut" (unless you are already very lean) and risk losing the new size you gained. 2 steps forward, 2 steps back. if you want to get really cut down, my suggestion would be to do 2 seperate cycles. give yourself at least a few months after the first cycle to eat enough to create an environment that will get your body used to holding the new size. remember that this is a game of patience. to actualize the goals i have for my physique, it can take a year...or years.

to answer your question about switching esters, yes you can do it. its easier to go from slow esters to fast ones. the key is timing and keeping the same general amount of hormone coming in. if you are running 500mg EW sust, then if you were to switch to prop, i would still use close to 500mg. 

also, on the note of "bulking" and "cutting", never let yourself get too fat in the bulking phase and your urge to cut wont be as great. i honestly look beach ready almost year round. i do get softer, less vascular and overall more watery in the off season, but not to the point that i look sloppy. that makes cutting easier and i can still see my abs at the end of a bulking phase. this all comes down to knowing exactly what you're eating. weigh it all out. know the exact aount of oz of meat you eat for each meal. the exact number of carbs and fats and then you can control exactly whats going on, using the mirror, pics, as well as how your clothes fit. if you start getting too out of control on a bulk, dial the carbs back a little. but always keep your protein high