Of course, I always recommend people allow enough time for things to potentially go wrong to help reduce stress, and certainly if you have Lounge access, there's always time for Lounge Time, but as a reference point:
I did have a friend fly last November on QF CNS-SYD connecting to a QF flight to NZ. Scheduled landing at T3 was 16:20 with the departure time for flight to CHC from T1 at 17:45, so a 1:25 connection time. I was mildly concerned for them, and monitored very closely their departure from CNS, arrival into SYD and remained in touch with them during their transit, ready to arm them with alternate flight options should they have missed their connection.
I also prepared them to navigate through T3 with photos and maps showing where they needed to head for the transit bus (they weren't terribly familiar with Sydney Airport), along with the scheduled bus transfer times (every 20 minutes at that time of day). Even with some mobility issues (nothing major, just a slow-mover), they managed to move with purpose, catch the 17:00 transit bus and make it to the gate with plenty of time to spare (at least 20 minutes I reckon). International Security and Smart Gates were quick to navigate through. Their baggage even made it across and arrived safely in CHC.
Admittedly, this is with a QF to QF connection, and therefore much easier with guaranteed through-checking of baggage etc.
If the originally booking was with Qantas, all on the one ticket, and if you were originally on JQ26, then yes, this is a domestic-sector of an International flight. The domestic passengers are known as "domestic-on-carriage" or DOC in the industry. It would've departed from the International Terminal in CNS and arrived at the International T1 Terminal in SYD. I'm not certain, however, how you would've transited in SYD based on it being a JQ to QF transfer.
Usually, domestic passengers on these flights are called D-Sticker pax, because they have a large sticker with D for Domestic on their boarding pass, which is meant to make getting out of the arriving International Terminal easier (through Immigration etc.).
Depending whether you did still need to collect your bags or not, then you still would've been in T1, and no need to transfer from T3 in SYD.
If your bags did happen to be automatically checked-through to SCL from JQ to QF, then you would've been able to use Transit Security, where, rather than exiting Airside through Immigration, you would've taken the paths to International Transit/Transfer, and ended up straight in the International Departure Lounge after going through Transit Security.
Anyway, these last comments are a moot point now, as you've been able to successfully move onto earlier Qantas flights. All the best.
