The engine itself will handle whatever the cooling system is designed for. If stock, go by the stock pressure rating. If aftermarket, then possibly 15lbs or so. You can find charts online that show the boiling point at different pressures for a particular mixture of coolant.
Another thing to be aware of is if you are using the stock temperature sender location, then the engine temperature is actually about 15 degrees higher at the thermostat housing. This is because the coolant still has to absorb heat from 3 more combustion chambers before it makes it to the thermostat. You're not going to keep the fan off in stop and go traffic. You might keep it off a little longer but it simply will not stay cool in that situation without the fan.
190 should be fine, if you want to bump it up too that. The engine will let you know when it is too hot by boiling over. If you install a temporary on/of switch, to override the computer, that will allow you to get home to readjust, if it does boil over at a higher setting.
My '88 Firebird uses somewhere around a 15lb system. The fan turns on at about 220. Below that, in normal operating temperature range, I can see the temperature rising pretty quickly by looking at the gauge, and via data logging software on a computer. By that observation, a 5 or 10 degree difference for the turn on point isn't going to buy much time. I think (might be wrong) the fan only turns on so high, in this instance, for emissions because at cruise, it will be around 200
Lawrenceville, GA