Pff, there are many ways to get to a nice looking clip with video and photo’s.
Although you can resize the images in PD, best is to set the photo’s in a separate “working” folder, and to crop these photos in the format of the final result (say 16x9). If you have a PhotoDirector or similar, (even Windows Photo app) which all in all may work faster.
If you then include all these media into your PD work space, these photo’s are already of the right format. No need to remove the background. While you are cropping the photo’s you can also brush them up a bit (if need be), the colours, the exposure, brightness etc.) so that this will not be needed in PD anymore.

The other method would be to add the photos, and cut/crop them in PD. If that is not possible, e.g. because you would cut off important parts of the image, you can put the image on the second track and put a colour board of your liking on track one.
What also is possible of course if to include the photo’s (one track two) and resize them such that they are nicely positioned on the screen and (in PIP designer) put a border (with width and colour) around them. You can in this fashion put more photos on screen at the same time, or swap them photo by photo.

To your question: Working in this way is usually faster then e.g. using the PD slide show creator. Which is yet another option: use the creator to create a clip that can (either via separate export or directly) included next to the video clips.