I used to work for a bbq concept owned by two of the partners who own The Steak Escape chain of cheese steak and fry restaurants. We went through literally tons of fresh cut fries a week. 1. Yes you can blanch fries days ahead. In fact it's better that way as you don't want to try to start the final fry with product that is still warm/hot from the blanch stage. The quicker you get your blanched fries down to refrigerator temp the better. Not unlike blanching any vegetable. 2. If I remember we blanched at 310 degrees and fried at 350-375. The blanch time was around 1 minute 10 seconds but I may not be remembering that step 100% correct. 3. Cut and blanch as early morning prep so you don't have your fryers tied up later when they should be making you money. 4. We used a peanut oil in our fryers. Makes great fried food of all sorts but you need to post it clearly due to food allergies. We also could get it a lot cheaper from Sam's than from distributors. 5. The kind of potatoes is rather important. They only dig potatoes once a year and then store them for sale for the remainder. If they aren't stored properly the starch will start to convert to sugar and that will brown too early in the blanching process. Also the water content is important. Too low and you get mealy fries, too high and the fries will battle your oil for temperature control. Get a very good relationship with a local produce company that knows their stuff. 6. The thermostat on your fryer is your friend if it's working correctly. Yes it "reacts" but that's its job. You cannot be standing there frying, selling, cooking, and manually controlling the temp. It kicks off when it comes back to it's set temp. Just don't overload your baskets and you'll be fine. 7. When you change and clean your fryers save a cup or so of the old fat provided it isn't rancid or burned. Brand new oil needs a little help to get started on the flavor profile. That said I have no idea how that works with beef tallow. Hope this helps.