Yes as you know userids change. Photopost I suggest you upgrade to 5.13 so you dont need to worry about having to rename files
You need to set both our products to the new config database settings to connect to vb
and enter the vb
license number there
You need to modify the settings tables to enter the correct integration prefix and cookie settings
Third as you know you will need to write a user import script to rewrite the userid's in the photos comments and category table( only for personal albums cattype a where the parent field is the user's id). Updating those 3 tables with the right userids for the usernames will fix photopost
Now reviewpost is someone more difficult since the userid is prepended to the images
You will need to do much the same as above with photopost yet you also need to rename the images with the correct userid on front.