First of all, ‘5G’ versus ‘5 GHz’ are two different things that are unrelated but often mixed up. One is the new (fifth) generation of networks for mobile telephony, which will work at higher frequencies with beam forming and will require many more transmitters.
The other is the wifi frequency of 5 GHz. Most modern wifi routers are dual band and broadcast two wifi networks: one at 2.4GHz and the other at 5GHz. The highest speed can be achieved on the 5GHz network by means of the AC-wifi standard. The 2.4GHz network has the best range.
If you prefer, switching off 5GHz will reduce wifi radiation from the router even more. You can do it from the JRS tab on the Wireless page. First set the Band selector to 5 GHz, then set Enable Radio to No and click on Apply at the bottom of the page.
The 2.4 GHz MUST be switched on for the Full Eco functionality to work properly. Therefore, when you turn off 2.4 GHz, the Full Eco mode will not be functional. The wifi will then not go into sleep mode. Nevertheless, the router still offers a 90% reduction in beacon pulse rate even when the wifi is active.
There is also the possibility to lower the transmit power for the 2.4 GHz frequency. The JRS firmware offers a fine tuning of the transmission power with ten steps, which allows you to reduce the peak values of the emitted 2.4 GHz radiation. The transmission power is inseparably linked to the range of the router, a physical fact that unfortunately cannot be changed. So it will reduce the range.
You can change the transmit power from the JRS tab on the Wireless page. First make sure the Band selector is set to 2.4 GHz. The transmission power is best set to the lowest value at which the desired wifi coverage is achieved reliably, and no higher. This depends on the size of your office or house, the type of walls and floors (wood, stone, or reinforced concrete), and the quality of the wifi receivers in the used laptops/tablets/mobile phones etc.
The wifi signal strength may affect download/upload speeds and stability. Just give it a try and see what is the lowest setting that still works for you. You may need to set the router to a different wifi channel in the Wireless -> General tab, to avoid interference from neighboring wifi routers and be able to have good range at a low transmit power. Using the Site Survey tab on the Wireless page, you can find out which channels are occupied.
The lowest possible setting is 4mW. The actual measured transmission power at that setting (measured by JRS) is a factor of 10-20x below the default setting. The lower the setting, the lower your exposure to electromagnetic radiation from the router.