GoPro workflow

Looking for advice about the best workflow for editing GoPro Hero4 footage in FCPX. I fly the camera under a drone, and the final output needs to be 1080p 25fps. I use all three FOV settings, Narrow (in 1080p mode) Medium and Wide and I usually shoot 2.7K and 50fps, using the Native colour setting in Protune and Flat colour profile.

I convert to 1080p 25fps Proxy on import as I find FCPX on my MacPro 6core 3.3GHz with 5770 1GB struggles working with anything higher. Am I right in thinking that when I export the master, FCPX will work from the original files, not the Proxy in the project? So if use slo-mo I get the benefit of the higher frame rate even though the working Proxy files are 25fps? Can I expect better results starting with 2.7K footage even though the final output will be 1080p, compared with shooting and staying at 1080p?

I'm using the FCP FX Fisheye filter, which seems to work pretty well, would you expect this to affect video quality much (apart from the slight cropping?)

many thanks

If you are editing with proxy files, and then export a master, the master file will use your proxies and create that quality of master. You will have to switch after editing is done to original/ optimized footage before you export in order to get a full quality master file.