Glad that helped.
For completeness: the campaign and scenario challenges only allow the choice of difficulty from three presets (Easy, Normal, Hard).
But when choosing "sandbox", an additional "custom" difficulty appears, allowing you to choose your own combination of values.
Default is "Normal", hence the 80% motoring appearing when you switched to custom.
___________Starting money_____Banks_____Demolition returns_____Private motoring
Easy _________15000____________4__________90%_________________60%
Normal _______12500_____________3__________50%_________________80%
Hard _________10000_____________2__________20%________________100%
Custom ____1000-100000________1-4_________5-90%______________20-100%
And I think I've seen a mod somewhere that allows a broader range of custom values. There was a humerous comment about it's 200% demolition returns providing an endless cash generator....
The "Bertrand" tram is far and away my default choice for early trams. And I find, even in 2000, it's the benchmark others are compared against. Carrying 28, cheap to buy and run, a single carriage length (so no length blockage problems), and quite acceptable speed, attractiveness, and reliability levels. It's an excellent choice whatever it's age. And perhaps it proves the point that the other trams are .... lacking? Maybe it's too good - reduce carrying capacity to 25, perhaps 22, and it's big advantage will vanish.
When I first started playing, the Prospecta Experimental became my default tram choice, until I realised it should not be available until very late (post 2000? 2010? - I'm not sure). So while 1920's trams and buses seemed OK because of the excellent DLC vehicles ignoring the timeline, this was obviously not realistic.
At the end of the day, it's possible to mod the stats to get exactly what you want, which is great.
But it's important to remember that rigorously setting vehicle capacities to their real values will simply break the game, because the rest of CiM is not realistic that way. The early buses and trams carrying 10 barely break even, and you have to have stop queues building up with red faces, because having enough vehicles to keep up with demand will have them running at a loss. Increasing to 12 feels right, maybe 14, but I suspect going beyond 15 will break the balance and make it trivial to earn a large profit. That would be a 50% increase in revenue from 50% more passengers, while costs remain exactly the same....