Personal opinion only

TBH, I still prefer the OG design over the three new ones. I like the modern style just kinda hard to tell how long or tall they are. While the new designs look okay on their own, they make the whole city look a bit weird when you zoom out. The new tree design is cute, but it doesn't really work next to the nature reserve since that area still uses the old trees. I wont even mention the new roads.

Mix and match might be the way to go, but the OG style is still the best IMO. That being said, the game is still awesome, and buying the new designs is a great way to support the dev. But if you just want your city to look cohesive, I would just stay with the og design.