There’s a book by Rosetti on designing jewellery with Rhino - mostly focused on v4, but applicable to v5. It can be a long-winded way to do it, but there’s nothing RG or Matrix do that can’t be done with “naked” Rhino - it just takes longer.
(can be a bit slow to arrive, the joy of international shipping at times)
I don’t know that TDM are planning to port RG to Mac, haven’t heard anything about it.
Much as I hate doing this (seems bad form) - there is a forum dedicated to 3D CAD for jewelry (well, they spell it different to me) - http://3dcadjewelry.com/ Not machine specific, but there’s a lot of Rhino users who can answer questions better than I can.