Tearing apart laptop batteries for the cells is a gamble at best, they have been used & abused for who knows how long. If you're only getting ~2000mah batteries, then it's not worth the weight penalty.
I use these for all kinds of things, from powering FPV ground station equipment, external supply to my Crossfire Tx, and long-range duration flights. I do build my own packs now, but I've done the research and gotten the correct equipment to do so safely and with quality cells.
https://www.imrbatteries.com/ is a good source of non-fake cells. The recommended method of building packs is spot welding nickel strips as hand soldering can damage them, reduce capacity, and maybe make fire. Speaking of fire, any battery with fire in the name is trying to tell you something! Max reliable capacity for 18650 cells is 3500mah, while slightly larger/heavier 20700 ones are 4250mah. There are a few oddball ones that claim higher, but with a low ampacity that makes them about useless for RC hobby use.
For a standard park flyer, these are likely a poor choice due to the high current draw. They are great for endurance and long-range flights where the current draw is kept around 4-5 amps. If you fly at or near the rated ampacity of the cells, you won't see much benefit due to voltage sag. They will handle the high amp spike during launch fine, just keep it as short as possible. I've had good luck with li-ion packs in smaller planes such as the ZOHD Nano Talon and Volantex Ranger G2, one hour flights are easy. I also have built a 3S 3P with 20700 4200mah cells that gives a 2m pusher FPV plane about 1.5 hours or more.
Charging is the same as normal lipos, but at a max rate of 1/2C. Discharge can safely go down to ~2.5v/cell, so you have to test your ESC at the lower voltages to ensure a lame voltage cutoff doesn't put your plane in the dirt before the battery is done.
Titan batteries make OK packs if you want to try these out, even if they don't work for your plane, they still are great power sources for other battery operated stuff.