At this point I have the Eaton hybrid supercapacitors, 220F, some specific solar panels I've tested (4.1V open circuit, so they naturally tap out at 3.6V below the diode, to keep the hybrid supercaps handy, with low part count.  No regulator is required to step around the hybrid supercapacitors, just a diode. 

I have prior experience with Espressif microcontrollers feeding their voltage systems back into the ADC with a voltage divider, so they can be programmed to go into deep sleep and then recover from intermittent power.  
Here's a video.  

In one of the images I've shared there's a Heltec WiFi Kit 32, hooked up to a Bosch pressure sensor, BMP280, but I may switch to another IoT such as the Adafruit ESP32-S2, which has the environmental sensor built in, or the Adafruit ESP32-S2 with TFT screen like the Heltec.   Initially it will not be important to conserve power, the main focus will be the software development for processing a research job with a mesh cluster.