I suspect the reason you're not getting an answer to this is because there is no one-size-fits-all answer. There are way too many variables. My advice is buy a lot and size it one you have everything plumbed. You do not want lines that are too long. You'll almost certainly want more than 4. I probably have at least 8-10.
One thing I see a lot on here - you don't need silicone before the brew kettle. Save yourself money and look into food safe urethane/ether which you can find on usplastics.com. Get a bigger diameter than 1/2" - 5/8" is ideal. A cheaper alternative to silicone is Tygon Tygoprene XL-60 and is more than sufficient for the hot side with the added benefit of being a bit more rigid than silicone.
Hope this helps.