Entering 2020, very little 5G is mmWave or low-band. The tall line in Alan Hadden's chart is 3.3-4.2 GHz. To its left is 2.5 GHz. To its right is 4.8 GHz, used by China Mobile.
Performance in mid-band is typically 100-400 Mbps down. Sprint's 5G network averaged 183 Mbps. (Open Signal) More than 400 Mbps is an exception; 1 Gbps great for advertising.
Low-band (the two leftmost) speeds are similar to and often lower than 4G. AT&T averaged 60 Mbps and T-Mobile 48 Mbps.
Millimeter-wave at Verizon is often over a gigabit. Open Signal found an average for 772 Mbps, probably in an area where Verizon is using only half of its 28 GHz spectrum. AT&T is using 39 GHz.
Japan and Korea are testing mmWave but few others.