Alright, resident JDM hotboi reporting in--
I would spring for the KW V3s if you're going that route (fully adjustable), or I'd recommend the CSG TEIN Flex A, but yeah coilovers are the way to go IMO. I've found most lowering spring setups to be too bouncy, and I'm 25 and drive a low car so I'm not a grandpa lmao.
As others have said, those wheels will work fine functionally. HOWEVER, if you care about looks/fitment, those probably aren't the move. When you're lowered those wheels will be "sucked in" so to speak because the offset isn't aggressive enough. I think the sweet spot on these cars w/ stock fenders is either 17x9 +35 for a performance-oriented setup or 18x9.5 +38 for full hotboi concave-face tastiness. In my opinion people bemoaning wider wheels as "heavy/unresponsive" is largely overblown-- if you're on coilovers and have a proper performance alignment w/ negative camber, running wide wheels on 255s up front is still plenty responsive. I'm on 18x9.5s with coilovers and my 2018 PP BRZ
does not have erectile dysfunction on the track. (Better driver mod will always make up more time than a skinnier wheel lol). & tire selection makes a much larger handling impact than wheel IMO. Definitely run square wheels & tires on these cars, don't even FW staggered setups, wider rears mess with the car's balance and turn in.
Here's my 18x9.5 +38 thicc boi for reference:
https://ibb.co/MfXRNVM
And here's a car with your wheel specs (WedsSport TC105):
http://www.ft86club.com/forums/showthread.php?t=121752
The 18x8 +43 don't look bad or anything, just not sporty/aggressive enough for my tastes.