Yeah it will change the speedo a touch, but it actually changes it so that it is spot on as the speed normally reads a little low from factory.
I would not be running 295s on an 8' rim, hence why I'm looking at running R8 Rims with 255/35/19s front and 295/30/19s rear.
I am getting a little traction loss but that's the reason I am looking at the R8 rims (I have 40:60 and up to 20:80 torque split). This is also why I have installed an LSD in the front diff.
On Stock position/size/turbos and Auto I would not run staggered but rather get the best set of 265 or 275 sticky rubber you can afford.