Editing Insta360 videos in FCP

My ancient iMac can't cope with doing any video editing and so I'm about to replace it with a Mac Studio and am trying to decide whether to buy Final Cut Pro or Adobe Premiere. I should point out that I am not a 'video editor', I don't have a YouTube channel etc and have no desire to do so. I am simply someone who owns a Insta360 One R 360 camera and who wants to do some reframing, editing and adding soundtracks beyond what is possible with the apps for the Insta360. Whilst my videos may be shot in 360 I don't want them displayed in 360, just in conventional HD or maybe 4K non 360.

I've borrowed a friends MBP who has FCP installed and he's allowed me to install a trial of Adobe Premiere as well to see which I like best.

I've been playing around for a week and I have to say that I much prefer editing conventional video (non 360) in FCP. However, it seems that Premiere might be better at 360 video, or at least better when it comes to videos shot on the One R. However, this is all new to me so maybe I'm missing something and other more knowledgeable people can clarify things for me.

So my Insta 360 One R produces 360 videos with a .insv extension. These files can be viewed and processed using either the Insta App on my iPhone or on the Desktop App. This is fairly good in that you can trim the start and end of clips, reframe and set all your keyframes. What it doesn't let you do is cut out anything in the middle of the clip or join clips together.

Insta360 suggest using the GoPro FX Reframe Plugin this not only allows you to reframe the clips but it also allows Premiere to read the .insv files.

The GoPro FX Reframe plugin isn't available for FCP and FCP can't read .insv files. This means that first I have to export the clips as MP4 files in the Insta360 Desktop App.

The things that don't make sense though are:

1. Once I've converted the files to MP4 using the H264 codec, in FCP, I go to Import Media, browse to the MP4 file but it appears as greyed out and it won't let me select it. However, if I drag the file from Finder into FCP, it loads it fine and it appears as a 360 video. So why won't it let me import it?
2. Is there a way to import/drag in .insv files without first having to convert them? It's quite time consuming having to convert the files first but I could probably live with it if I had to.
3. In Premiere you use the GoPro FX reframe plugin and you can set keyframes and adjust all the parameters. However, you can still do this in FCP without the plugin so does the plugin give you access to any other controls that aren't there natively in FCP?