Welcome to the site FG911! I too have had better luck hunting later in the season. There are pros and cons and you have to weigh out all of the factors such as hunting pressure, weather and nesting conditions.
In regard to decoys, I have used them in the early seasons but stay away from them later on. I like to play cat and mouse with the tom enticing him to look for that hen (me). In the past, I’ve had a few toms get hung up out of shooting range once they saw my decoy. They may be a little wiser due to hunting pressure or sometimes I think they want to draw that hen (decoy) to them so they strut and spin… strut and spin just out of range. Then they get bored and walk off looking for a more receptive hen.
In regard to loads – I agree with PowerFred. Pattern your gun to see what load works best for you. I have a 12 ga. browning gold hunter and shoot #5’s – heavy weight. I also use a turkey choke.
Calls? I too use a slate call. To me it’s all about matching the volume to the distance of the tom. I’m able to accomplish this more effectively with a slate call. However, I think it also has to do with confidence. Work with what you think is best for you.
It won’t be long…