My opinion after a bit of research is that you should always take Loss damage waiver (LDW) and Supplemenatry Liability insurance (SLI) options.
I discovered additional info too, such as LIS insurance which is always included by law but varies state-to-state and sometimes covers very little.
My own travel insurance company were oddly clueless about US car rental insurance options. I'd have thought it is a common question. I rang another company and got the info I needed though.
And, don't get me started about Californias new child car seat laws!!