I need some expert advice...

I am looking at some wheels that are 18x8.5". The offsets are:
et20 and et42.

According to wheel offset calculator, when compare to the stock wheel, the et20 will be:

The clearance from strut housing to the inside of the wheel will be 4mm MORE
The outside edge of the wheel will EXTEND an extra 16mm

The main thing I am worry about is the outside edge of the wheel will EXTEND an extra 16mm, which is about 0.62in. This should still be acceptable right?

Should I stay with stock tire size or can I upgrade to a bigger size?

I curently have the performance model with 18x8 all around.

Thanks!