USB-C charger interoperability

The answer is yes “both ways” from a “safe” perspective …

… but you’ll probably find that the smaller adaptors just can’t keep up w/ your Mac’s power demand … and that it’s battery SoC will still be decreasing. (albeit at a slower rate)

The 20W power adaptor (w/ USB-PD) is certainly at THE bare minimum to even consider attempting.

The Mac might also throttle it’s performance if it “sees” a smaller power adaptor; I’m honestly not sure how that “piece” fits.

FWIW, I’ve used a 20W adaptor on the road w/ my own MBP for a couple of years now.

It can’t do a “lot” … but it CAN keep up w/ “most” tasks needed when away from the desk/dock.

For what it’s worth. 🤫

And I remember how my AST “386” was the envy of the office.