Caster is about spindle inclination. An easy way to think of increased caster is like this: your front end setup and alignment is like a mountain bike front end - little or no caster). It is easy to turn and nimble but you can’t take your hands off the handlebars. It’s not stable and you will crash if you try riding without your hands on the bars. A car with a lot of caster is like a road going bicycle ( for the lack a better term - a 10-speed). That bike has lazy steering, but it is very stable. You can take your hands off the bars and it still will track straight ahead, without too much fear of tipping over.
With stock a-arms you cannot shim it enough to get 5+ degrees of caster. You won’t even come close without cutting and welding suspension pieces (been there, done that..
). That’s where aftermarket a-arms enter the equation. They’re built with more base caster.
With a small tire, and a relatively low HP car you might want to really consider the disadvantage of coil overs on the front. Big conventional coils store a lot of energy. Coil overs? Not much. You probably need suspension travel to make your car hook. You won’t get much travel and stored energy with coil overs. If it was my car, I’d avoid coil overs if at all possible.
Hope that helps a bit…
Wayne