I have a 3/4 in. pex water line coming out of my meter to my house. I would like "T" that line and run a 1 in. pipe (or larger) off it. My question is, will I see an increase in flow in the larger pipe since the water is already traveling thought a 3/4 in pipe? I would like more pressure/flow so I can run my larger sprinklers.
As "benefit" you are thinking of more flow and or pressure.
That will not happen, since flow and pressure are already regulated in the supply line (3/4 inch).
However, you might experience a pressure drop.
The distance for the sprinkler depends on sprinkler design and incommoding pressure.
You can make it spray further by reducing the nozzle size.
If the line from the meter to the valve box is long, the line will reduce flow and pressure somewhat. A larger line will reduce it less. Whether it's enough to matter is hard to predict. In my area installers always use 1 inch from meter to valve box. Nobody has a 1 inch meter. I don't know why 1 inch is used but on a fixed price irrigation install I assume it gets the installer better results.