Hi. There are many different types of RNAV equipment available to 146 operators. The most worst to use was the Trimble system (know as the ‘tremble’ to long suffering crews). Operators later standardised on various versions of the GNS system. All were capable of BRNAV, but ISTR only the GNS-XLS Enhanced was capable of being approved for RNAV procedures.
I not sure that the UNS version modelled for the JF146 was ever standard fit for the aircraft. I’ve used later version of the UNS (on corporate jets) that were capable of full RNAV including approach, but I don't think the early models were any more than BRNAV capable.
From a ‘Simming’ viewpoint, if the required SID/STAR is in the database, I would use it - but check that the various waypoints are correct first. btw, when using using RNAV routes/approaches/departures, other than removal as part of a routing, it is not permitted to amend or extra insert waypoints.