My personal bias - when training spro calibration, I have a view that some parameters are more fundamental than others. Here is a rough model, in descending order of priority (reasons):
- dry dose (costing starts here)
- brew ratio (dilution ... particularly a concern for milk drinks / latte artists)
- grind size (impacts rate of cooking)
- pressure profile (cannot separate from grind size: impacts flow rate)
- temperature (impacts flavour more, flow rate less)
- time (least important)
