Just ordered a set of 18x9.5 +45 wheels, need suspension advise
 

Currently I’m running RCE Yellow springs on factory shocks, I was told in order to fit the new wheels I would have to go with coilovers in order to have space to clear the wider wheels. Is this true? If so will Tein Flex Z provide ample room?

This is true: You need coils to fit 18x9.5 +45 wheels. And yes the Flex Z will work for what you need. They were on my list while I was shopping for coils. They get good reviews.

Anyone cross shop Tein Flex Z with ST coilovers? Similar price, I’ve told ST are ore comfortable but no custom damping adjusments. Flex Z has custom damping but tend to make noises?

I have 18 X 9.5 +38, at +45 you'll need coilovers. It's because the spring perch is too wide and you'll be rubbing it.

I have tein flex A which is the same thing as Flex Z just a Hydraulic Bumpstop, and you'll have enough clearance. You'll also be able to run 255 35 tires no problems. 265 is when you'll start rubbing.

For 17x9 +35 wheels and 245/40/17 tires, can i stay with my current suspension setup of RCE Yellow springs and stock shocks?

Yes.