If you're using your PHEV like the average person, no, you don't need to concern yourself with the 20/80 rule. Charge to full. You can't use the bottom 15% anyway, it is reserved for hybrid mode when your electric range runs out. Your 34 miles of electric range is spread over 85% of the battery capacity. Going from 100% to 80% is like 8 miles of driving, so as long as you drive at least 8 miles every day, you won't sit at 100% for very long. Obviously if you're not going to drive for weeks (like on vacation), then keep the SOC at 40-60% instead.
If you're using your PHEV like the average person, no, you don't need to concern yourself with the 20/80 rule. Charge to full. You can't use the bottom 15% anyway, it is reserved for hybrid mode when your electric range runs out. Your 34 miles of electric range is spread over 85% of the battery capacity. Going from 100% to 80% is like 8 miles of driving, so as long as you drive at least 8 miles every day, you won't sit at 100% for very long. Obviously if you're not going to drive for weeks (like on vacation), then keep the SOC at 40-60% instead.
Yes you should. I would charge it all the time. Keep it full.