You have a bit of a slope - be glad, because it offers you opportunities to think "out of the box." Setting a level to place a flatland house on it will not lead to good architecture. Think with the slope rather than against it and get experienced local help (architect).
Topic of staggered roof surfaces & knee wall - good idea:
My parents built a house in 1970 with a staggered gable roof similar to the image suggestion by to comply with the eaves height requirement towards the street. Inside, however, it is not a split-level. The knee wall to the garden is over 2m high.
Topic terrace:
The terrace for cozy sitting, barbecuing, etc. does not necessarily have to be on the same level as the ground floor. Slightly modulating the terrain and having a small path leading to it can be very nice, perhaps a bit less practical, but absolutely lovable and worth living.
Topic split-level:
From an ergonomic point of view and in terms of space utilization, one can certainly argue about a few steps here and there - nonetheless, there are highly attractive solutions. I would not set dogmas here and instead look around to see what is possible and what an architect comes up with.