FYI as additional information: due to WIFI problems I changed a outside monitor box from OpiZero-256 (old version) to OpiZero2Plus with H3 processor. After turning down all unnecessary interfaces in the fex file, the H3 CPU idles now at a temperature 1-5 deg C higher than ambient, with minimal power consumption. In the weather-proof closed box (140x80x50 mm) there is a 18B20 sensor close to the OpiZero board, on the H3 I have a small 14x14 mm heat sink.
The initial setup with the 'old' OpiZero-256 survived even full sunshine and a box temperature of ~75 C. The old WIFI worked fine until the system went to sleep and usually never woke up.