You're going to get varying opinions on this. Ultimately, I believe it's a personal choice based on how much in personal assets you want to protect etc. Of course there are other methods of financing besides commercial loans such as private money but I would think that has even higher rates (but for maybe a shorter term).
Anyway, for me the interest rate didn't matter as much cause I largely use private loans so I went ahead with the LLC. I only have one property so far so sometimes I wonder if it was the right choice, but I'm glad I did it because it gives me a little more peace of mind.
I've heard various things on umbrella insurance. Some say do it, while others say that if you do it, it signals to those potentially filling a lawsuit that you do have assets to protect. It's a catch 22, and I haven't quite decided myself how to move forward with that yet.
Ideally I think you'd want to utilize both (LLC + umbrella insurance).