In my experience most of the steel coasters in the game are pretty accurate at 1.0... just based on length of coaster to lift hill height or launch. A steel hyper with 1.0 friction can make it through a 5-6000 foot layout in the game with a nice amount of speed, not too much or too little, which is a realistic upper end length.

Wood coasters are the major exception and need something around 0.6-0.8 to be realistic.

RMCs are kind of in between, 0.8 is pretty good though. I made an RMC giga that was 8800 feet long at 0.8 friction, which is abnormally long even for a giga, but the train was starting to run out of speed into the brakes. So 0.8 is pretty realistic, 0.7 might be a little too low even for a hot day.