Internet is a finicky thing. What you should be getting depends a lot on what you pay for, what device you have, and the equipment you're using, not to mention the infrastructure you don't control. Without more detailed information, it's hard to say. But, that said, your download and upload speeds are more than enough to do practically anything you should want without much of an issue.

The key words in your plan are certainly “up to”.

Actual speed is going to be highly variable depending on your provider, bandwidth available at your specific location, even weather.

This could also be limited by your router, and/or what band you're on. 2.4GHz WiFi is indeed limited to around 300-400 Mbps whereas 5GHz can reach speeds in excess of gigabit. It can also change depending on how far from the router you are and what sort of obstructions are between you and the router.

As an Australian, that is 20x faster then ud ever get here so Id say yes but obvs it might be slow for where u r lol

On Wifi 5 with a 2x2 stream you should see around 300-400 Mbps on a speedtest with a strong signal.

PHY rate (the 1.2 Gbps you mentioned) is different from the throughput you'll get, and they also usually lie about that number by adding both the 2.4ghz and 5ghz bands together.

Yes, it's totally normal, unless your router is WiFi 6, because it can reach quite the maximum speed of your connection, and so the speedtest you've posted con be a little lower then what you can expect from a WiFi 6 router (the speed depends a lot on the distance from your router and the obstacles between your smartphone and the router).

Most providers give you a "UP TO X Mb/s" number which is not what u get most of the time. Usually there is a lower minimum limit in the contract or law that they have to deliver, at least in germany thats how it works.