IIRC, KQ also showed an additional bag as a benefit.

Anyway, I'm at CGK, doing an I-I transfer TG-GA on separate tickets. So my experience will probably be interesting for a couple of you.
Just before immigration, there's a transfer desk (next to the VoA payment desk) and an escalator to a security checkpoint on the upper floor. I already had my GA boarding, so I just went upstairs.
The security officer there asked me if I had contacted the transfer desk: "No, there was nobody there, but I already have the boarding pass for my next flight."
"Go back down, I will call them, you have to be cleared by immigration"
Someone arrived, asked how long it was until my next flight, looked my boarding pass and then told me to go to immigration. (Assumption: This was probably the easiest way for them to deal with me, and since there was enough time, they didn't want to do any extra work - fair enough.)
Went to the immigration counter and the border office seemed a bit overwhelmed by the situation. She made a phone call and then told me to go back and pay for a visa on arrival.
"But why, I don't want to enter Indonesia, I already have my boarding pass on my phone...?"
"You can only use the transfer channel if both flights are on a single ticket. And you can't use your mobile boarding pass, it's Garuda policy, you need a printed boarding pass. So you're going to have to clear immigration and customs and then go upstairs to the checkin desk."
Went back to the VoA desk (next to the transfer desk), paid for my visa IDR 524,500 - about $33, then went back to immigration.
At customs, they wanted to see the QR code for the digital customs declaration, so make sure you have that. They didn't ask for a health declaration.
Went upstairs (this was quite far) to the Garuda checkin desk, where the agent didn't really understand what had happened: "The mobile boarding pass on your phone is sufficient for us:"
Anyway, got a printed boarding pass, went to the security checkpoint. Asked to use the fast track, which had "SKY PRORITY" written above it. Like in China, got a laugh (!) from the guy guarding the checkpoint: "Business class only!"
Cleared security, then got to the e-gates. Tried 3-4 different e-gates, none of them recognized my passport. This cost me another good 5 minutes. Went to an officer in the end and then I was through.

Here's the timeline:

14min - taxi to gate (very long taxi)
4min - waiting for jetbridge
2min - deplaning
12min - discussion with security checkpoint/transfer desk, walk to immigration
10min - queue at immigration (filling out the customs declaration on my phone while waiting in line)
6min - buying visa, clearing immigration
12min - going upstairs to checkin desk (long walk, slow escalators)
2min - checkin
2min - walk to security
8min - clear security
5min - clear immigration

And then there can be quite a walk to your gate (probably easily 10-15 minutes if your flight departs from the other end of the terminal).
Also note that the airport was basically empty. There were at most 2 people ahead of me, there usually wasn't a wait at all. So the times above are the absolute minimum, I don't think you could do better than this.
Last time I was here, I had to wait at immigration for 45 minutes or so.

TL;DR: Book everything on a single ticket if you want to be able to use the transfer channel. But even then, you'd probably have to speak to the transfer desk, which can take time. I don't have experience with this.
If you have separate tickets, do yourselves a favor and pay for your visa online, so you don't have to wait. Also do the digital customs declaration in advance (QR code).
Then you can maybe (if all your stars align) make it in about 1 hour from gate to gate, if you don't have checked bags and there are no lines anywhere. But if you have to queue, then that won't be enough time.
I would say you should budget at least 2 hours between your flights, ideally more.