How to import product content different for each store view (translations/multilingual)?

Apparently the solution is pretty simple. Too bad there is no word about it in official docs. My second approach in OP is almost correct, but you have to import all store views together in one import, including default. Separate import will reset field data for all store views and keep only the one's in last import. Difference with 1.x is that sku must be set for each store view. So the correct Magento 2 way should be something like this:

sku,store_view_code,name
1111,,"Default name"
1111,et,"Translated name"
1111,ru,"Another translation"

Note that this CSV will not work as initial import, but only as update of already existing product. You need to add required attributes for initial insert.