It's not a clear cut thing. Scenary doesn't have as big an impact as coasters or other trackrides. Flatrides do not have much impact either. Paths and coasters have the biggest impact. Each console has a different limit based on the specs of that console. The hard drive doesn't really have much to do with it. Planet coaster is heavy on ram, CPU and GPU.
Yeah but you can imagine that people are not gonna pay 50 dollars for the game then 10 dollars for each DlC pack and you can't use it all it's same when you would bring rollercoaster tycoon 2. But you can't use the Expansion packs but pay full price. As it is now it should not cost more then 25 dollars. Because you can't use it full as on pc. And DLC pack should be 50%. Then it's fair. Oh my xbox one x I have also limit of 20-25 depends on what I build but for me this is to boring and I am done building a park in 2 hours or less. Then I can start over again but now I just keep playing on pc.