What is your favorite way to power your portable projects?

I am on the fence between 2 options and both have pros and cons. You can use a single Li-ion cell with a decent capacity that works well with TP4056, but you will likely need to step it up to stable 5v. Or you can use 2 Li-ion cells in series. Many boards can regulate it themselves, so chances are you will not have to step it down yourself. But in this case charging it as a bit trickier, having to get some S2 BMS, worry about them being on same voltage etc.