If planning a big battery pack build one potential problem with big brand batteries is price and availability. On the other hand there are some lesser known OEMs making decent cells with good availability and price. PLB and Lishen are two of them. Lishen makes the LiitoKala rewrapped Lii-40A, a run-of-the-mill 3C max 4000mAh 21700 cell (HKJ reviewed). It could be interesting given its low price (AliExpress 8 piece pack example). Maybe in Alibaba better deals can be made when going big quantities and/or even buy first brand OEM cells, but no experience in this respect.
Cheers ^:)