Our tap water CH is around 200-250 ppm and TA around 110.
It's possible to manage your pool chemistry with CH up to around 1000 ppm. It take a TA around 60-70 and continuous pH monitoring to keep CSI within range. And after a couple years, a full drain/refill is warranted.
Your best bet would be to have a water softener and use that soft water for your autofill. This will keep your CH in check. With our hard water, your CH will go up 250 to 400 ppm or more yearly do to evaporation.
There is no "target" CH - you can use that in PM to see how much to drain when CH gets high. That 'target' setting should be your current CH until it gets high enough to need a drain/refill. You need to use the CH you have and adjust other parameters to keep CSI in range. In PoolMath, Settings, turn on Track CSI, Track Water Temperature and Track Combined Chlorine.
The goal is to keep CSI around 0.00 - best to keep slightly negative, in the 0.00 to -0.30 (negative 0.30) range to minimize calcium scaling.