The Target does matter, but you have to leave the paths and files with the macros QtCreator created, which make use of it. When you have you don't have to specify if it's the lite or full version, since you're done changing the Target directly.

I don't know how to remove a package before installing another one. I don't think QA team will make such a prerm script even pass.

You have to focus keeping the paid version working, so that is the package which must keep its package name and item id, otherwise users which have paid it won't be pleased. So you should remove the lite version, change the package name and resubmit it. The content item id is already another one, isn't it?