Concrete is best at 5". We use 5" for thermal properties, rebar placement and 3/4"X3/4" scoring tool does better if concrete is 5". 4" is ok, however, 4" nominal or a 2X4 which is less than 4". The 4'X4' scored joints will help with cracking. Cracking is not necessarily a bad look if it is not cracking due to bad concrete. Integral color with carnauba wax burned in on first go with buffer and then two more applications and final buff shine.