@Patrick M.
Managing your properties well and legally protecting you are two different topics as you know.
I think having an umbrella coverage on your property may be good enough if your portfolio is small. The bank account wise, it does not really matter if the account is business or individual. It is usually for the banks because they can offer the customers different services. If you use the account as a regular checking account, there will not be any difference. But it is significantly better than mingling your real estate business with your personal accounts. Some of my users do it but I alway highly recommend them to have a separate bank account.
Of course it is better to use a property management software because it makes your property management work much easier and it keeps your record safely.
However, if it is one or two properties and you file Schedule E, excel sheet can be good enough.
Just remember to keep the record of "Everything" in case your accountant or even IRS requests evidences.
One thing about umbrella insurance tho.
Umbrella is an insurance. The insurance company will fight and do whatever it takes not to pay for the damage you are claiming. If the damage exceeds your property's capacity, it will come to you personally.
If you have a LLC, if a really really bad thing happened, the worst case scenario, you just lose the LLC.
Umbrella insurance is a great product to protect you but you should be aware of the difference.
Good luck on your business!!!