If me and my buddy shoot the same kind of gun, do we both need to pattern or will they shoot the same? Assuming same load, choke,etc.
The harmonics of the individual barrels will come into plat slightly. There won't be enough of a percentage difference to warrant worrying with it. The issue you should be concerned with is Point of Aim and Point of Impact being the same(gun shooting where you are looking)
Put the LM Cremator in and leave it, when you get to consistently hitting the birds(90% of your shots) then put the IM version in and leave it
The shells you have now will work for now, when they are gone, buy some from Roger's Sporting goods, they run sales on the premium loads throughout the year