@hkgcat I've answered some of your questions on another thread, so I just answer the ones haven't been answered.
I googled Huawei E5577C, it seems that you can use it, but I'm not 100% sure. You can just buy a a card and try, since it's only $33. I think the speed is okay, considering the speed test I've done was almost 40 Mbps with SoSIM. I do zoom call as well, and never have any problem.
I'm also using a pocket wifi thingy. Yes, it could get hot sometimes, but I'm not that concern, since it's not my cellphone. And unlike normal broadband router, now I turn it off when I go to sleep. But other than that, it seems okay for me. I keep it plugged, just like a normal broadband router, cause I'm not using it as pocket wifi to carry when I go out.
Q2: I believe someone asked the same question, and it should be free to receive only.
Q3: I've answer on other thread, now you can top up with credit card through the app, from anywhere.
I believe I read on other thread that you live in Gold Coast, I actually live opposite Phase 2 right now, and if you like, we could meet up for you to try the sim card.