They operate in completely different scenarios. They’re the same shape, but they’re a different set of hardware, constraints, accessibility, need to be scheduled in a different way to account for traffic, different safety concerns, different signalling systems, different distances, different surroundings.
Again I sorta see what you mean, but feel you’re massively over simplifying this.
(For me, the big thing about trams and trains and subways, etc is that the track is a kind of social construct - the track tells me that eventually a vehicle will come for me - no need to really worry about timetables, etc. A bus, a bus may come, maybe it won't. It's all psychoillogical but it's there the same.)
The fundamental operational principle is different. Trams operate (typically, on street running sections) on sight - they are responsible for monitoring traffic, and stoping if necessary. Contrast with the block-based approach used for trains, especially in combination with Euro-style positive train control systems.
The second sentence is partially true: they do have different modes of operation.
But no, they don’t face entirely the same issues. Trains should hopefully never routinely encounter cars sharing their track and they don’t have to make tight turns to follow existing roadways.
Well then there's no difference between overground and underground trains. But it's pretty clear that there are different issues facing building new metro lines.
There are different modes of operation that differentiate them but fundamentaly they are all trains and face the same issues