Low latency wireless monitor solution (2021)
I’ll answer the lowest latency which is at odds with your minimal and cheapest requirements. (From the Good, Cheap, Fast - pick any two triad)

Use LunaDisplay to transmit wirelessly to an iPad Pro that mirrors using a hardware cable to the display of your choice. The USB-C connector to a display that charges the iPad is the lowest latency in my testing.
AirPlay to an AppleTV hard wired via HDMI is second lowest latency.
TeamViewer comes in third place on Big Sur 11.2.2 using a ghost 4K HDMI adapter with commodity USB-C to HDMI adapters. This is the most expensive option since you need two “computers” and a second ghost display.

Dongles and hard wires are faster than everything and the LunaDisplay hardware effectively reduces the latency of wireless options.