I've installed/replaced and serviced many septic systems. Including the ones on 2 of the 3 houses I have lived in. The house I bought with my first wife was extensive and a complete replacement. Demolish and drain old tank, install new tank 1000' closer to the house, laterals, drainfield manifold heading four 125' perforated schedule 40 drain runs. Used the neighbor's perc test. That was the first time I ever operated a backhoe. Took a week. The wife and I had to use a chemical toilet for a week and it was horrible.
Perc test is over rated. There was no such animal when 90% of septic systems were installed. As with anything, overbuild it and you'll be fine. 500' of drainfield for 2 people was definitely overkill. The drain field in the house I live in right now was installed in the early 60s and the performance and water lines in the tank assure me the drain field is just fine. Even after having been submerged by the river several times for days at a time. Most likely, like every other drain field in this neighborhood, it is a coil of perforated corrugated plastic. Other than replacing the lateral when I rebuilt the house it has been fine for over 60 years now. I live in a special flood way and technically cannot replace a septic if it fails. I also have a 6' privacy fence and could replace the entire system in about 8 hours easily.
The rules for septic systems in the county I live in were oppressive. They have recently relaxed them quite a bit after the realization that the rules were pointless and did nothing other than cost people a lot of money. My sister in law had to pay 30k for a system with a couple grinders and pumps and all that. It had to be engineered and installed by a county licensed company. In the 10 years she has lived there that system has failed twice.
I have installed systems that consisted of schedule 40 and 55 gallon drums in hunting cabins. I have repaired or replaced more laterals than I can remember. Septic systems are very simple and effective. And by the time the water from the drainfield hits ground water it's 90% drinkable.