I think even the free tier allows for original quality but its been years since I was on it. You only get like 15 GB of space though as well.

Self hosted you could use Plex to automatically upload all photos to your computer then download as needed to the other one.

Personally I use Google photos to do this and it works great but will probably require you to get a subscription depending on the size of your library.

My personal phone is android with a work iPhone and I want to transfer things over sometimes so I set up my work phone to upload as well.