Not the question I asked but ok I guess
the answer to your question is yes: the 100W limit is not in the cable or charger but in the rest of the type-C (Thunderbolt) ports on your 16", they are "only" USB PD version 3.0 as mandated by TB4 specs, with a maximum power profile of 20V5A (100W). Apple's white type-C charger cable then is also capped at 100W but you can use a 3rd party 240W cable and still only get 100W out of the type-C ports of the 16", even when plugged into a 140W charger.
The MagSafe port of the 16", then the MagSafe cable are otherwise both PD 3.1, with a max profile of 28V5A thus 140W total is possible. The charger side of course also have to support this but for now Apple's 140W power brick is no longer the only product that does this (it was when new).
Depending on what you want for the 3rd party charger, IMO for sake of cable confusion and cost, it currently is not worth it to deal with 140W at least on the road, because it takes a PD3.1 charger which is still rare and costly, and then you must use the MagSafe cable which is obviously not interchangeable with anything else.