It is okay to edit your video content in a different app than Instagram, but make sure any text you add, you do so in the Instagram editing section that pops up when you create your reel. Instagram can detect when you have edited in another app and will be less likely to push your post, so when you add edits within the app you will increase the reach of your posts.

Additional information: https://www.youtube.com/watch?v=1n1VnbiOw3I