Which location can hit those speed?
I'm at clementi area and speed no much difference to 4G
5G NSA is like: your phone camps on a 4G spectrum, for example band 3. When your phone thinks you need higher bandwidth, it automatically adds another 5G aggregaton.
5G SA is like: your phone always camps on 5G spectrum, not using 4G at all.
So during normal use, if using NSA, your phone will actually use 4G most of the time. Only when doing speed tests, 5G will kick in.
That's why when running a speed test on NSA, first few seconds will only get maybe 100Mbps down. After a few seconds, 5G is connected, can get 600Mbps+ or even 1Gbps