Please be so kind as to read my full post before responding.
Thank you for your consideration.
As far as I can tell, the height of the expanded DropDown and ComboBox controls, and the height of individual selectable options, seem to only depend on the (font) Size property of the DropDown/ComboBox control. User feedback from our PowerApps users suggests that many users prefer to have an larger height of individual options (for chubby fingers) while maintaining font Size (for example for limited width considerations), i.e. having (font) Size smaller than would be necessary for sufficient option height based solely on font Size.
Please add something like a "LineHeight" property (of the Label and TextInput controls) to be able to adjust the height of (invidividual lines of) options in expanded ComboBox and DropDown controls.
Apologies if I have overlooked an already posted idea on the same topic.