With 5G mmWave operating at >30 GHz, it's understandable why 5G runs so hot. Hopefully low and mid band 5G is not so power hungry. Same reason why 5 GHz WiFi is fast, but more power hungry than 2.4.
Unless you have more than 20 devices on your home network, you likely won't benefit from WiFi 6 (though it will still be helpful at airports, stadiums, etc). I would replace my router with WiFi 6 when my current one dies, but wouldn't rush to get it. 5G on the other hand, if it's available where you live, could be a reason to upgrade. I'm hoping T-Mobile lights up the low band 5G soon for fast in building speeds.
https://www.cnet.com/news/when-are-...dgets-coming-what-the-manufacturers-say-wifi/
Google WiFi product manager: "In order for users to benefit from Wi-Fi 6's higher speeds, all devices in the home would also need to have an 11AX chip and be no more than 15 feet away from the router, A user also needs to have more than 50 connected devices on their home network (the average Google Wifi user currently has 18) to notice a significant difference between a Wi-Fi 5 and a Wi-Fi 6 router."