so how I did it for a snug fit was (I used 30mm coin cases because I didnt like how small the 25mm felt in the hand)

Front photo facing upfoam gasket thingNFC StickerBottom photo facing down

If your 25mm cases allow room for a chip inside and will still close and fit snug these are the exact size for a 25mm sticker here: https://www.amazon.com/dp/B0752CYJF3

they look like this: https://i.imgur.com/3BgMoMw.png

and lastly to be honest with you coin cases are so cheap so they are a bit spungie sometimes so a small dab of super glue would probably hold it super secure, I know some older amiibo makers recomend using Airtight coin cases which snap tightly close but those can cost up to hundreds of dollars which is a bit more than I would like to pay

as far as your conerns go make sure you measure them, I opened up that template and measured it and it looks like they would actually print at 30mm, a lot of times you have to resize it properly in PS then create a new 8.5x11 blank photo then paste your resized photos into there to maintain the print size, I dont know if there is a better way to do this but that's how I did it to maintain the size, and as far as Walgreens goes thats just what their phototechs say or whatever, I would print 1 sheet to see how it is, have a ruler with you and make sure its 25mm and if you like it print the rest if not go home and tinker with it then come back, I know that is a bit of a pain in the ass but at least that way youll get exactly what you want without wasting a bunch of money or print

for a visual example this is what I mean https://i.imgur.com/0s7jx45.jpg, the templates I used came in 35mm, I resized them to 30mm and exported but it still printed at full size (Notice the labels on top of the print the middle one says "small") so after doing the process with the new photo like i mentioned above then they printed out correctly, and as you can see I have a lot of room on the borders of the page even with 30mm coins so for 25mm if you resize properly you should have no issue with 8x10 paper.