I'm thinking about whether I should get springs or coilover.
If I decide to switch to 19" wheel, am I gonna have any problem with the wheelcap, if yes, should I go with coilover instead?

 

If you keep the constant diameter the same with the correct size tire on the 19's they shouldn't be no different than stock, which of course stock height shows wheelgap, personally I'd go with the coilovers for the winter time so you wont act as a snow plow...