There is two sides to observe:
- The router.
- The client device (your phone or what ever device).
If the specifications of both sides do match, then the maximum performance shall at least in theory be possible.
Regarding 802.11ax: the standard is defined but equipment does not need to support all features of the standard and manufacturers can be very unclear in what their products do actually support.
The 802.11ax standard does support the following (and more):
- Up to 8 data streams. Most equipment does support only 1, 2 or 3 data streams.
- Four bandwidths: 20 MHz, 40 MHz, 80 MHz and 160 MHz. Most common are 40 MHz and 80 MHz.
- Three frequency bands: 2.4 GHz, 5 GHz and 6 GHz. Most common are 2.4 GHz and 5 GHz, equipment supporting 6 GHz is slowly entering the market.
- For 5 GHz and 6 GHz, the following data rates can be reached with a single data stream (more data streams add up to each other):
- 20 MHz: 143.4 Mbps.
- 40 MHz: 286.8 Mbps.
- 80 MHz: 600.5 Mbps.
- 160 MHz: 1201 Mbps.
Be aware that most client devices can connect to a single frequency out of 2.4 GHz, 5 GHz and 6 GHz at a time. Routers are often advertised with the sum of all data streams of all frequency bands.
With the above you can calculate what maximum (theorethical) throughput you can expect by checking the bandwidth and the number of data streams that both ends of the connection do support.
Conditions, distance and disturbance at the given location usually result in lower throughputs.
Mixing older and newer standards (e.g. 802.11n with 802.11ax equipment on the same network) can cause performance degradadtion.
Hardware of different manufacturers can also cause less performance when used together, usually that will enhance (or get worse...) when new drivers for the hardware are released.