Takeaway: 95+% of 5G is lowband (< 1800 MHz or mid-band (2500-4200 MHz.)
Asia, TMobile US, and much of Europe is mid-band.80-200 MHz of spectrum usually delivers 100-400 Mbps.
Low-band (AT&T, much of DT & other European, runs at 4G speeds and sometimes lower. See AT&T data below.
Millimeter wave often does 500 Mbps and a gigabit, but will be rare for years.
Gigabit and 10 gigabit 5G speeds are mostly a fantasy outside the lab. That will be true almost everywhere until 2022-2023, when large-scale millimeter wave deployments begin. Outside of Asia and possibly Verizon, gigabit speeds will be uncommon until late in the decade.
Spectrum and the number of cells/antennas mostly determine speed. Every engineer knows 5G is little faster than 4G. The 80-200 MHz of new mid-band spectrum is where the speeds come from, whether 4G or 5G.