It must be unique to your house, because when constructed properly, the plumbing is the same whether it goes to the city, or to the septic.
When I run into a toilet that is adjusted properly yet has a weak flush, then I just tell the people that it needs to be replaced with a better flushing model.
Forty years ago people would demineralize their toilets with acid, to help restore the original flush.
My tank holds 4 gallons. It is a low-flow installed in ‘85. It has no mineral buildup after 27 years. It has fairly new guts that work perfectly. It takes at least 2 flushes to do the job and has since day one. The only design that would change the equation is one that used more water.