What additional liability coverage beyond umbrella coverage and LLCs should I consider?

What are the advantages of having one (arguably there are no costs that can't also be obtained with an umbrella liability insurance policy) versus the costs (yearly registrations, extra paperwork, startup costs, more expensive mortgage options)? 

I just have good insurance, plus an umbrella policy.

Just get a big enough umbrella. 

Couple that with a good umbrella policy and that should be all the protection most people need.

In Feb of this year, we purchased a ST vacation rental condo on the beach in FL.We currently have a $1MM umbrella policy and started a relationship with an asset preservation attorney because we are going to start looking for another long term rental in the north metro atlanta area to try the BRRRR method.He is suggesting we change our JT Rev Tst to two indv Irrev tsts (with us as the beneficiaries) -> the trusts will be the owners of a holding company, multi member LLC. 

I will not be able to purchase properties in cash and will likely start off by taking mortgages out on properties using my name so let's not discuss corporate veils as that's another discussion and intend on holding an umbrella insurance policy.

My question is can I write off a portion of my umbrella insurance policy?

In your situation, get good umbrella insurance for now.

I use C Corporations and S Corporations and get umbrella insurance.