I’m talking strictly a home. I worked in home mortgage lending for 18 years and we never had any of the issues you discussed come up. There were a few occasions where there were liens placed from parties that were not paid, but those were usually the sellers issue anyway, so they had to be paid prior to getting a clear title. If there is a recorded lease option that still shows, then yes, the seller would have to follow up on that, but you would assume, of course crap happens, that when the seller purchased the property, that they received a clear title. Nothing is perfect, but I don’t see the need to pay a realtor 6% to do work I can do myself.
You are not required to pay a 6% commission. In California, as in any state, the amount to be paid is negotiable. I have very often worked for people on a consulting fee basis based on the estimated amount of time they are paying for my expertise.
If you have the expertise and understand all the legal ramifications and risks, do it yourself. But you have nothing to lose and likely something to gain by giving many brokers an open listing and agree to pay a fee above the net price you are seeking. You will have many more people working for you while still having the ability to sell yourself.