About machetes and chopping wood. I recall with some distaste an episode in the piney woods of Oaxaca. gnawing my way through a log bout 6-8 inches diameter that blocked our 'roadway,'. it took forever, and i was wishing I had either a decent ax or some sort of a saw. None of out three vehicles had any such - a grievous error. Still I did whittle my way through the obstacle and we made camp.
Silky saws and similar "pruning" saws are quite different from the traditional buck saws used by early lumberjacks and I doubt that trappers downed any redwoods, or at least only a very small number.
I rarely backpack with them, but i keep a hatchet and saw in my vehicle. My absolute favorite tool of this nature is a pulaski - think single bit ax joined with a grub hoe. Give your fire crew those and shovels and your wildfire will be contained.
Hikermor, being a fellow SoCal boy, I'm disappointed in that last paragraph.
You know good and well that time, fortuitous rain, and Mother Nature do more good on stopping wild fires than a crew with pulaskis and a brush truck. Maybe if it's in the initial stages...
I would agree that most firewood - if there's actually wood for a fire - can be found with minimal collecting effort. I'd also submit that if you're cutting up large pieces into small pieces, you're probably better off walking a bit more for more small stuff. I don't think the juice is worth the squeeze.
Regarding machetes. Probably too thin for actual hard wood harvesting; great for softer stuff. Khukris could conceivably be used, as they're thicker, but IME they can glance off or spin in the hand rather quickly. I'm not a fan of batoning wood (remember that whole 'right tool for the job?') but a large knife is obviously key there. While a machete could work, I think most are still a bit thin for that. A good 8-12" Scandi knife or similar would be good if that's your preferred method of wood processing.
Going to the redwoods. If you pull up some of the few old pics remaining, you'll see guys with 2-head axes and 20' saws in the same picture. Obviously they can compliment each other.
In the end, it's OP's choice. Both are good options, both depend on his environment, skill and preference.