Hello, thank you for supporting us ^^
To answer you, the Kickstarter version is the same as the itch and Steam version. The only difference being that backer will have access for free to a DLC we plan to release later this year. Where non backers will have to pay for it.
As for the 4th pictures slot for the affinity characters, you have to first finish the main story and increase affinity to the max, then they will be available. The only thing missing now, is the king's affinity, and it should be available late August.
Hope this answers your questions :)