Is there a way to select and edit media in groups?

I am trying to make a slideshow using Adobe Premiere Rush.  I failed terribly trying to use PhotoShop and LightRoom to make them.  I have figured out how to add all the images I want in the slideshow to the timeline.  But, the aspect ratios are too few.  16:9, 9:16, 4:5, and 1:1 are all that is offered.  I shoot in 2:3 and 3:2.  I hope that they add those into the mix soon.  But, I have figured out how to choose an image and in the transformation tab to select the option to "make it fit" and the whole image is viewable.  Is there any way to choose all the images at one time and make them fit?  It seems when I choose more than one image, the transformation selections go grey and I can't choose anything!  Am I doing something wrong?  I can't possibly be expected to choose "make it fit" for every single image one by one, am I?  Your help is much appreciated.