Since 2020 t14/t16 thinkpads no longer have a user swappable battery without removing screws. So you can get a 50wh standard battery or 82wh. Before 2020 you could get a slightly larger 96wh battery with a bump out, plus the small internal battery.

A power bank with a usb-c 65w pd will work for most laptops. Many of these will be 100wh/20000mah or 150wh/30000mah, to meet airplane limits.