Yep, cages are great on a track with the proper safety equipment but not so much on the street.
I'll throw my opinion out there on the harnesses. Honestly if you think that most of your time in the car will be on the street I wouldn't run harnesses. I recently had to drive my "track" car, which has 6-point harnesses, to work for a couple of weeks and it was not fun. The whole latching and tightening multiple belts then not being able to move around and/or reach things part of harnesses sucks for the street. For my street car, I just had a local auto upholstery shop rebuild my factory belts with new webbing. They look great, work just like new, and are (IMO) more than adequate, safety wise, for weekend cruises and occasional trips to the office.
BTW both of my cars are running stock rebuilt turbo F54/P90 long blocks with a stock turbo on the street motor and a T04B/T3 hybrid on the race motor and have (IMO) more than enough power for their intended applications. If you are not looking for big, expensive power but want a little more grunt you may want to look into a mildly modified l28et swap.