Thermostats - high flow vs standard flow - now I am confused

When the thermostat opens it allows the coolant to flow into the top of the rad, down thru the core and then back into the engine block.
If I got this right you are asking about flow. If the flow is too fast it hasn't had time to cool in the rad core so a higher temp will result.
That's why some have a overheat problem when not using a thermostat.Something has to regulate the flow(restrict).
You may try the high flow T-stat first and see if the temps are to you liking.Too hot ? then replace with a standard flow.
Old school guys would drill the T-stat plate out giving more flow or replace with a metal disc with a 5/8'' hole to slow the coolant down as necessary.