Coming from iTunes to Windows Kodi

I had a sizable collection of music and videos on my old Mac mini and played it through my TV using an Apple TV. My wife and I are going to be moving into an RV in a few months, so I wanted something smaller and less power hungry to play those files on. I tried getting a Raspberry Pi with Kodi to work and just couldn’t make it happen and got frustrated and gave up.

But a few months ago, I had planned on using a Lenovo Stick PC to run an iTunes server on it and play it through the Apple TV. I had some problems with the initial external HDD, so I had given up on that. But now I’m back to it. And I realized, what the hell do I need an Apple TV for anyway, when I can play all the files through Kodi, directly form the stick pc instead of streaming them through our wifi and having yet another device sucking the precious battery power.

But of my files, most of my movies are in mp4 or m4v format. Will these play in Kodi or should I convert them to something else before I even bother copying them to the new external HDD. I have an HDD formatted as exFAT, which should be fine in Windows 10. I also have a file converter that will convert video and music to just about any format I can use, so what would be the best and smallest format to use and still be 1080p for the ones that originally were?

Also, I know Kodi won’t play AAC locked music that I had bought through iTunes years ago, but I think I converted those as well to m4a. I might just set my laptop up to convert every friggin song into mp3 or something. I’m not an audiophile. so mp3s really do sound good enough to me.

And finally, is there a way to shrink some of the files down? Most are in the 800-900 mb size, but some are 2 or 3 gb. I’d like to get each movie under 1gb if possible. I’m using Smart Converter Pro 2 on macOS for that.