Camaro and autocross question

Hi, I have a 2017 Camaro SS 1LE and since I am about to need to get new tires I am thinking about going down to 19inch from the OEM 20inch that I have now. My question is, if I want to stay in F Street I need to get the same width as OEM so that means I need to get 19*10F and 19*11R and the offset will need to stay +/- 7mm from OEM (i..e., ET20F and ET43R). Did I get that right? I can try to get as wide as possible tires that can fit in these wheels.

I think APEX Arc-8 is available in 19*10 and 19*11 and with OEM offset but I am wondering if there are better options that won't cost much more than APEX? Tires wise I think some people are able to get 305/30/19F and 315/30/19R with the 10inch wide F and 11inch wide R. I think for 200TW (or higher) options it's basically Michelin PS4S (which is what I have now) and Falken RT660. Am I missing anything? What are the popular choice to run Camaro SS 1LE in FStreet?

Thanks all. 

I don't know anything about your wheels specifically but your understanding of the allowances is right. RE71RS in 285/35/19 is probably the best choice for overall speed. Falkens will probably last longer but likely won't be quite as fast despite being slightly wider. Michelins even slower but might last longer and will be better for normal driving.

You will have to make sure that the wheels will clear your brake calipers.  It's a pretty tight fit with the factory 20's for the 1LE Brembos.