Best kind of bicycle for lower back issues?
I have a touring bike and I find it quite comfortable. But them again, I don't have back issues. It's a bit more upright than most road bikes, and possibly more upright than some hybrids I've seen, as long as I'm riding on the hoods. Try to find a place that rents bikes or will let you have an extended trial ride in order to determine if it would help fix your issues. Spending $100 renting a few different models for a few hours at a time could save you a lot of money and help you find a bike that's comfortable for you.