[2020] Does having all buildings unlocked lead to better planning?

It might, but it also might not. It really comes down to what works for you, so I suggest trying it out. This game can be modded in different directions to customize the way you play, so that you get more of the stuff you enjoy. I recommend just experimenting and finding what works for you - there's really no wrong way to play the game as long as you have fun. :)