Yes, if you feel some utility or set of functions that u can use across different projects than u can bundeled in one jar.
like for instace.
setText,scrollTo these kind of functions u can use across different files. so u can bundle them.
and regarding cucumber files, U need to create runCucke files which points to ur testNG xml, which eventually trigger your tests.
I will upload cucumber+Appium project soon to my github page.
Thanks,
Priyank Shah