My advice- Relax and enjoy the propect of a short comfortable internal flight Downunder. JQ, QF or Virgin will be more than OK Im sure (based on my numerous experiences after spending 20 years living in (and out) of Australia). Virgin have nice leather seats, QF and JQ ? - not sure as Im normally up the front in QF on Avios points. Jetstar can be anal (overly strict) about carry on weight (7kg?). All airlines appear to have reasonably happy proactive staff ( they are living in Austrralia after all where the weather and the minimum wage are not too bad and penalty rates apply at weekends etc to many workers (1.5 x on Sat, 2x on Sun).Only aerosols are forbidden at security and after security (Qantas at least) you just wander off to the gate (5 mins) and board when requested about 30 mins before departure ( comfortable gate boarding areas where you can buy a coffee if you wish whilst waiting). I think QF and VA give you a free snack and drink unlike some in Europe (BA please note!) . Probably too much information but domestic in Oz is a pleasure in my experience compared to some flights here in Europe. One tip is that if you wish to avoid a 3 and 3 config (possible middle seat - although as OW Ruby you should be able to select your seat ahead of the pack, look for the A330 which flies several times a day giving you 2 plus 2 seating = - 0800, 1000, 1300 departures are examples (on a Saturday at least). I shall be doing the same route in reverse in 2 weeks and am currently pontificating over the long haul ticket from Europe - Y and save, J and spend, F and treat (upgrade with voucher) FWP I know. Enjoy Australia.
OF