1) On the Mac, you can certainly store the photos in Lightroom and edit them in RAW Power. RAW Power can work as a file browser, so if you can point RAW Power to the directory where you store your files, then it can view and edit them. It stores the adjustment data elsewhere (not with the original).
2) The app has some ability to work with a portrait photo. There is an adjustment called Depth Effect, which lets you adjust the highlights and shadows of the foreground and background independently. It also lets you adjust the depth mask so you can control what is “foreground” and what is “background”. It does not allow you to change which portrait mode is used.
In general, edit parameters are not portable between imaging apps from different companies. Shadows + 50% in RAW Power is different from Shadows + 50% in LR. Even White Balance and Exposure use different algorithms.
And the RAW decodes are different, so even if exposure was the same algorithm, Apple and Adobe render the unadjusted RAWs differently so you are starting from different points.
Edits in RAW Power are stored in one of two places. If you use the Photo library, they are stored there and sync over iCloud Photos. If you are using the File browser, then there is no syncing solution; the files are stored in the app’s “sandbox” folder which is buried in your home directory.