No comment on the inverter, but just the wire size is a complicated question with a large amount of power and a long way to transmit.
First, you want to transmit at the max voltage you can manage to reduce current as much as possible. There are two fundamental ways to approach the issue:
1. Transmit with DC. On whatever device is interfacing directly with the solar panels, heavily bias your selection to the max voltage input rating. Then connect as many panels as you can in series without exceeding that rating.
2. Transmit with AC. Put your inverters as close to the panels as possible, then do the long run with AC. At 120 VAC you'd be looking at 150 amps max current, and a 150 amp residential service requires 1ga copper wire. YMMV because residential service is usually shorter than 200 ft.
My guess is a deep dive will show that 2 is the only feasible solution for a variety of reasons, but I'm not going to do the hours of research to nail that down.
Option 2A is to consider a transformer in the middle and bump it up to a higher voltage to save money on wire, then convert it back down at the house. But the labrynth of adding such a device in the middle of a grid tie system is too much for me to even start investigating.
But to answer the question you should have asked: If you're asking these questions, you should absolutely not be building a DIY 18kw grid tie system with 200ft of power transmission system. You don't even know if charge controllers and inverters are related to shade or not, and your mention of the charge controllers leaves doubt of whether you know that they are only applicable to systems with a battery. Sizing wiring is one of the most basic tasks you can complete in solar design. And besides the several major complexities grid tie introduces, if you get it wrong you could kill someone. Hell at this scale - whether or not you grid tie - killing yourself or burning down your house is a very real possibility for 'minor' mistakes like an under torqued nut. It sounds like you've got a good deal on the panels or something and figure "how hard can it be?" Well watch a few Will Prowse videos, listen to how incredibly knowledgeable he is, and then realize that he refuses to post videos about grid tie because he doesn't know enough about it.
Please go build a 500W off grid system. Learn everything you can about it. Spec every component yourself, understand exactly why you are doing it and be prepared to prove you did it to standard. Ask questions on the forum, but to gain understanding not to just find the "right" component. Then add it to the grid, using the same approach. Then scale it up to 2000W or so. At this point you can move it to the remote location and develop your transmission system. Then and only then should you consider scaling up to a massive system like 18kW.
