@stepside
as for the highest yielding strain, that would probably be Northern Lights XL Autoflowering, its a really strong genetics, easy to grow and resulting in really sturdy plants.
The next one in line would probably be White Widow XL Autoflowering. Automated version of the White Widow mother we work with results in above average yields without to much hassle.
As for outdoors and more harsh climate grows, I'd reccommend Green AK XL Autoflowering, this strain grows really well and is really popular in the Eastern Europe, where the climate gets a bit more hard.
Feel free to visit the Autoflowering section of our website:
https://www.zambeza.com/30-autoflowering-cannabis-seeds
If you have any further questions, let us know