'ideal' is a handful. ask anyone who their 'ideal' mate is, and you'll get as many different answers as number of people you ask!
given your back road requirement, i would suggest looking at what @
grumpysnapper has done to mod his car for a no-compromises australian back roads driver.
https://www.ft86club.com/forums/sear...rchid=27488654
i would generally suggest the '18 over a '13 due to overall improvements made in the '16 update, though a ts over a 'standard' model could be up for debate yet. the '13 also had some minor teething issues being the very first model year for the platform, which may or may not show up in more rigorous driving.
and while you've definitively decided on a brz over an fr-s/86, know that besides some stick-on badges, and different stylistic plastic on the front end, all of these cars are built side by side in the same factory, with the exact same mechanicals and sub structure, so anything that has been done or can be done to any other of those models is a possibility for your [future] brz as well.