Three things worth knowing properly.
Short, specific and written from the app rather than around it. Each answers its question in the first paragraph and then explains why.
Importing XMP presets on iPhone
Three routes, all from the Presets screen: the iOS Files picker, which covers iCloud Drive and anything else Files can see; an in-app Google Drive sign-in; and an in-app OneDrive sign-in. Neither cloud app needs to be installed, and each route can take several presets — or a whole folder — in one pass.
RAW and ProRAW with a live preset
With a look active and RAW on, xMosaique saves exactly two files: the 48 MP ProRAW DNG holding untouched sensor data, and the photo with the preset applied. Turn the look off and you get the DNG alone. The DNG is never touched — the preset is applied to the second file, so the negative stays a negative.
Film grain and halation
Grain is one of four film-stock structures, applied at a size relative to the frame rather than to the pixel grid. Halation is a red or orange bloom that appears only past a brightness threshold you set. Both render in the viewfinder and in the saved file through identical maths, so what you frame is what is written.