It depends what your are doing. Some chips can get down to about 100uw to maintain associated and send small amounts of data. I'm not sure how they would compare at 2mbit or how the range would compare.

I'd say about 10mA (about 30-40mW at 3.3V) is the lower limit if you go a bit out of Wifi spec to save some power with current wifi modules in the common market for Microcontrollers and IOT applications.

What devices have that?

I've measured that on an ESP32, specifically, using various power saving measures and substracting the chip's own consumption. Though Wifi is atleast 99% of power consumption on a sensor device with not much else going on.

Interesting. Thanks for replies. I was hoping to find something I could add a small battery to and it could run a small vpn client as long as it had wifi connection. Ideally for months or years without maintenance if possible.

To save power, it could even wake up at certain times, say 5 min a day, then go back to sleep until that time window arrives again.

I can do all of the software I just don't know what hardware I should be looking at.