1- i1display Studio is a Color Munki Display AFAIK. It “should” use the same unlock code so Argyll should work with it. Ask in ArgyllCMS mailist for details if other people does not know if they share the same unlock code
2- You’ll need the more expensive version if you want to use HW calibration in some models like Eizo, NEC, Viewsonic, Dell, Benq, LG… If you buy the cheaper one… fotget HW calibraytion (internal calibration)
Also since it is like a Munki Display… it’s slower. Big test charts for LUT3D will be painful with the cheaper one.
It may be enough for you, just pointing its limitations