modern or practical
Well said, modern and practical often stand in contradiction...
Do you mean modern as the adjective related to the noun fashion or the adjective related to the noun modernity?
Focusing too much on fashion in a new building unfortunately means that it becomes "outdated" very quickly ...but if the money is right, go ahead and rebuild after five years...
So very practical is a network of empty conduits, also to windows and doors (consider soundproofing), water and drain connections in every room, walk-in shower / bathtub, alternatives to stairs, basically everything that can meet future usage requirements. Take a look under "barrier-free," you'll find many ideas that make life easier... also in old age or if mobility restrictions occur at a younger age...
Very practical are also double or two washbasins, bidet in the bathroom and odor extraction directly at the toilet bowl..., with several family members (possibly planned later) a second bathroom / toilet
And then not to forget, everything that makes you more independent and lowers primary energy consumption, use of renewable energies, solar/geothermal energy use, combined heat and power plant with floor, wall, and ceiling heating (especially very practical in the bathroom) ... effective systems for ventilation, natural and artificial lighting, shading, etc.
There are many possibilities, however, your requirement profile / anticipated usage behavior, not only now but also in the future, and your budget framework are likely to be decisive...