Hello Musketeer1234,
Recents is a default camera album that cannot be removed. By default, it stores all photos and sorts them by what photos were added recently. Usually this will be time-based but obviously if you add a lot of photos at once this can appear out of order. To view photos in order you should click on Library.
I'm not too familiar with WhatsApp or transferring from Android to iPhone. Could you search your albums and see if a "WhatsApp" album was created. This would be a good way of distinguishing which are which. Again, everything goes in the Library and within the Recents album. There is no way to remove them from Recents, but have them in other albums.
If there is no album, you can try click on any photo within the Recents album and clicking that `i` icon. It might tell you here if the photo was from WhatsApp or not, along with telling you other data about the photo / video taken.
I hope this helps!