As you can see title is rendered outside the card, directly on the GUI background.
All other cards renders title on the card background being a part of the card.
Here are the same sensors but displayed using custom:vertical-stack-in-card card.
Unfortunately there is another drawback: there is no spacing between cards. is it possible somehow to
achieve the both from those two cards: title like in the second one and spacing like in the first one?
Both vertical and horizontal stacks put the title outside the card. It’s the only way to get a title outside the card. It makes sense because stacks are a series of cards, where would you put a title for a series of separate cards?
The vertical-in-stack card is a custom card that takes x number of cards and turns them into a single card, hence why the title is inside the card.
If you want to add spacing inside the vertical-in-stack-card, then you should use card mod and add padding to each card.