Do I need a separate trimmer for line-ups and beard work?

Yes, according to repeated comments on r/SelfBarber — clippers cut bulk hair, trimmers (T-blade) handle outlines and beard detailing. Sets like the Novah, Fadeking, VGRPRO, and Jack & Rose include both, which reviewers appreciate; the Wahl Magic Clip is sold as a clipper only and is typically paired with a separate detailer.