18x10 ET50 rear wheel fitment please

[benr999]

I'm a new owner and member and looking into getting new wheels. I've been looking through the many posts regarding proper wheel fitment (+ getting a flush look) and wondering if someone can help me with my questions:

will 18x10 ET50 needs spacer on the rear (how much spacer I'll need to clear and
will 275x35x18 tires be a good fit (clearance?)
front is 18x9 ET45 (fitment ok?)

Front will get 225x40x18 and rear gets 275x35x18 tires

I have an '02 Boxster S currently running the stock 17" setup and all stock suspension (I may be lowering it a little at some point)

thank you in advance.