I’m currently using Layout, but it’s not great on iPad (only works in comp mode). Looking for something clean and simple that works on both. There are hundreds of these apps, but many of them seem cheap and gawdy.
I do already have shortcuts for combining photos, but they don’t allow you to adjust and crop individual pictures.
I use Diptic.
Dchar, I love, love, love 
Procreate for a mere $9.99. No subscription! The regular collage app will take you to the cleaners and I think are rather cheap looking.
Art Studio is also the same price. It’s a similar app. I like it but I prefer Procreate.
It’s actually an art app but you can do collages. There CAN be a bit of a learning curve but there doesn’t have to be. When I started, I didn’t know what I was doing pretty much and I was quite happy with the results.
There is a FREE manual in the Apple Books store too!
There are a plethora of videos to show you how on YouTube. I usually just experiment.
Have you had any experience using art apps? Or collage or scrapbook apps? There use to be a LOT of scrapbook apps about six years ago but they disappeared.
I like using Scrapgirls for lovely background papers. You can add embellishments (like flowers), word art, nice lettering, all sorts of stuff to accent your collage so you wind up with more than just a few photos. For instance, you can add a lil journaling card describing your photos or including information about your friends, family, place, item (you name it).
The pages turn out much nicer than just photos. I’d rather add the stuff I get from Scrapgirls than pay a monthly fee to these collage apps. Honestly, I couldn’t find one that was decent. And they all wanted a subscription. You don’t own anything too. I looked hard.
Scrapgirls has sales all the time. Scrapgirls.com
Let me know how it goes or if you need help! (Maybe you can help me. LOL!)
Whatever you do, do NOT buy, subscribe to Linea Sketch. They have THE biggest scam going on in the App Store. Unreal.
I would either recommend picollage or google photos.
What is the problem with Linea?
I bought the app. Almost immediately afterward they moved to subscription. Only for one “free” year can you access your work! It’s hardly free. You just paid for it!
Then you won’t even be able to get into the app! Any other app grandfathers you in or lets you use the app as it was when you BOUGHT it!
Now it is $40 to purchase the app. Only I bought it a long time ago! A couple of years…
Such contempt for their customers, it just boggles my mind! It is practically tangible. Read the feedback.
And ProCreate is a far superior app as is ArtStudio. You can buy BOTH to own and have $20 left over.
Collages are easy to set up. Procreate has a free Guide in Books. There are loads of videos on YouTube.
Línea has THE worst business model I’ve ever seen. Someone over there must be a wee bit greedy. No idea what they are going to think of next to try to swindle people nice enough to send them money.
The app itself is mediocre.