Here's a list of Queensland plan descriptions:
QLD Lands Valid Plan Descriptions
I've never heard "fty".
In terms of crown land, you're looking for "CP" (Crown Plan) or possibly "WD" (Working Drawing) for older parcels - sometimes it will be both.
RP (Registered Plan) is an older description, when the common types were CP, RP, BUP (Building Units Plan) and GTP (Group Titles Plan), or one of the derivations of that - such as GRP (Group Titles Plan of Resubdivision). BUP and GTP were used for strata developments - typically BUP for highrise type units, and GTP for townhouse type developments.
When the current automated titling system came in, the move was made to SP (Survey Plan) for pretty much everything.
So, when you see RP you can be pretty confident its a flatland-type property. With an SP it could be anything.