90 min is legal MCT so fine if single ticket, and 99% of the time you will make it. For separat tickets you want a bit more leeway (mostly for late arrival/late deplaning due to no gate available at BNE). For single ticket the checkin deadlines don't apply, but for QF domestic it is 30 min in any case -- so you have 60 min from landing to clear immigration/customs. As stated you drop off bags at the international terminal after customs for your domestic QF flight, so no need to carry them between terminals. There is a free bus landside to the domestic terminal which takes 5 min and typically runs every 10 min during prime time, so not that onerous to go the 2km between terminals.