CGK has always worked well for me arriving on QF and departing on GA domestic (&vice versa) as terminal transfer has simply been required me to walk outside and go upstairs and back in the terminal. Ive usually managed lounge access with either QF or GA and enjoyed the JAL lounge and GA lounges. I prefer the JAS lounge compared to other option that QF give (to the right of the JAL lounge). They have beer on tap and spirits available. Food hasn't always been the best but passable. The lounge atmosphere has always been very quiet and it is comfy. Always east to find a seat prior to the QF flight.
Outside the lounge you are very limited. Some international coffee chains might be a non-lounge option but with access to the lounge Ive never had to try them out.
Ive been caught once at CGK prior to check-in opening (a few hours) for my international flight - torture. If you have a long transit, Ive heard that going to the Sheraton and using their hotel lobby as a lounge is a good option - a thread somewhere on AFF.