I have done all 3 options mentioned above and I personally would choose company vehicle if it still allows for normal personal use.

The option I was in where I was paid mileage and given a company car, the miles paid was a reduced rate rate like 0.28 to 0.32 cents a mile based on vehicle class. The IRS has a very defined set of rules for this case. You can write it off unless it exceeds something like 2 percent of gross income and you can only write off what is in excess of the 2 percent. I paid for all the normal stuff like oil, tires etc.

Also, most (maybe not all) require the vehicle you drive for company purposes to be a maximum of 5 years old and less than 150k in miles.

Some of this might be outdated as it was 9 years ago when I was in company vehicles.

And yes, most companies require 1 million in liability insurance to drive on site. 5MM is higher than I have ever seen but I don't doubt it. Most of the time the individual picks up the first 300k then the company has a blanket for the remainder. This is my experience working for speciality chemical companies driving onto site of the biggest corporations in the world, paper, chemical and oil industry.