Hi, I have been filming in 4K 30 FPS on my mini 2 , when I load the clips to my iPad Pro the footage seems judery and not smooth, I have tried using iMovie software some are ok and some aren't. Is it better to film in 2.7k ? Or use better software?

Check on a desktop just to make sure it's not the ipad, maybe it can't decode the video fast enough (though I think it should be able to). Now that the firmware allows 2.7k at 60fps I really consider that a much better option. I don't think most people can tell the difference on a 4k display especially upscaled properly. However if you are shooting in order to do a 4x zoom for  1080p then stick with 4k.

I find my iPad Pro (second gen) jitters and pauses for a split second a couple of times while editing or viewing 4k drone footage.
As mentioned above transfer to your PC or Mac and see how it goes.

I found saving them to photos from files often shows the real video performance however, if its a first gen iPad Pro, it may simply be lacking some power.

Difficult if you don’t have a pc or Mac

Pretty sure that your video will play without any problem with a pc or mac. Some of the lightweight editors like [urlhttps://acemovi.tuneskit.com/video-editor/]TunesKit AceMovi[/url] is good enough to handle 4k videos.