How long is a Non-O visa valid for in Thailand, and is insurance required?

A non-O visa is good for 90 days and can be extended for 1 year if you meet the requirements, generally having 400,000₿ in a Thai bank account in your name only.

Some consulates require you to have insurance to get a 90 day non-O visa in your home country, and some do not.

You could try getting a non-O for 90 days and then applying for a 60 day visiting Thai family extension giving you 150 days.

Or you could get single entry tourist visa which would give you 60 days, and you can apply for a 30 day extension to this. After those 90 days you can apply for the 60 day visiting Thai family extension, giving you a different way to achieve 150 days.