I was wondering if it is worth it to redirect non existing m.example.com links that are being displayed in Google, or if it is better to just delete these from Google (if that is possible)?
Redirect them only if there is a suitable/corresponding page to redirect to. Otherwise, if these pages literally do not exist anymore then it is better to return a meaningful 404 message, perhaps guiding them to pages they might find useful.
Providing you are returning a 404 status then, in time, Google will drop these pages from its index.
If you think content is really related than do 301 redirection. Do not redirect to homepage, instead create meaningful 404 Error page.
Yes, you can remove those results from search result by using 410 code. I did not recommended to use 404 pages, because Google think, may be this content will be back, may be user redirect this pages to another URL. So Google do not immediately remove 404 pages from search result.
So, if you place some content in your site, and further you just remove it, and if you think, it will never come again, then I strongly recommended to use 410 against 404, because it remove those pages fast from search result compare to 404.