If using two different types of cells in a 2p setup, then you want only one kind in each series string, then parallel those two strings.
For actual pack build info, including BMS and charging options, I'd recommend looking thru the many 18650 pack build threads, as there are a lot of ways to do it, and each has it's good and bad points. Once you see how they did it, and how it turned out for each, then you can decide which way to do it for yours.
It's a lot of reading, but it is also a lot of information that will help you understand the process and reasons better.
Because of the way people choose to word things, there's no single search that will find just the pack builds, but this onesearch.php?keywords=18650&terms=all&author=&sc=1&sf=titleonly&sk=t&sd=d&sr=topics&st=0&ch=300&t=0&submit=Search
is most likely to find most of them, even though a lot of other less relevant threads will also come up (but most can be dismissed based on titles without reading any of the thread, if you don't need that info).