Still playing too, have 7 drivers, and two garages, one large, one medium, the reason your money shoots up if you quick travel is that you lose 12 hours, great for earning money if youre lazy, but your own productivity goes.
Got almost all drivers on Valiant F16s, but i have two MAN TGX and a Scania 620, not yet level 25 so waiting on the last engine unlock to upgrade it.
Covered about 50% of the map in exploration, havent visited all cities yet, since i dont trust my drivers to cover loan instalments or earn enough to buy a new truck and driver every few days like i can with driving, so im still taking jobs everywhere and not free roaming yet.
Quiky told me and its true if you give them the best engines they will do better, not sure about anything else but engine wise go for top shelf and the drivers level up faster and earn better
Also, running real company mod 1.4, which replaces a lot of trailer skins and logos, and no speed limit mod. I stopped using the physics mod since it felt too weird and was causing the truck to slide too easy.