I do not have the S42 but would consider it with upgrades specified.
For charging boards I recently finished a light using one. I get 0.350mA drain with one green indicator LED in the SW button. There is also a red for charge indicator.
And forget the Micro USB plug too, I want to see a Waterproof magnetic connector like I have integrated into my Lil’ light.
The ME4056 Nanjing Micro One Electronics Inc. Charge controller chip is on the little board I used. It shuts off to a Low current state state.
I do not understand most of the technical electronics stuff but here is a link to a post I made on the boards I bought. Datasheets are linked too.
ME4056 Tiny charge board similar to TP4056
Link to the Clone M3 build specs in post #11