Mig welder upgrades

[Weld65]

I would like to upgrade my current mig welder with a new mig gun.
The problem is ..........
I bought the mig welder several years ago & I didn't do any
research prior to purchasing it.
I ended up buying a Chicago Electric flux mig welder 150...........
I know,...

[Weld65]

On a typical mig welder......
Should the contact tip extend pass the gas nozzle or
should the tip be recessed into the nozzle?
And.... how far should the tip extend or be recessed? 1/8", 3/16"?

Thanks

[Weld65]

When mig welding, typical what regulated gas pressure
should be used?

Thanks