Yes.
is probably your simplest (and safest) option. But you would want to check what the Librem 14’s actual power requirement is to make sure that 100W covers it e.g. look at the existing AC-DC converter.
It is unclear whether you only want to “charge” the Librem 14 or actually operate it - but either way USB-C is a good option.
If you have a cigarette lighter output (is that the “Car Power Output”?) then you can get an adapter to USB-C but you would definitely need to check what power the Librem 14 requires and then get an adapter that is rated for the job. (I have such an adapter but that’s only for my Librem 5 and, simultaneously, Mrs Wade’s iPhone so the power requirement is modest.)