Does it suffice to give the expiation for an oath (kaffarat al-yameen) to "Mawa'id al-Rahman" (charity iftar meals), knowing that those who break their fast there are poor but not indigent (miskin)?

It is permissible to pay the food expiation money to trustworthy charitable organizations that oversee "Rahman's tables" (charitable meals), if those who attend them are poor and needy, provided that the feeding is done twice to the same ten people. If you were to undertake the feeding yourself, it would be better. There is no difference between feeding the poor and the needy, as they are synonymous when mentioned individually.