All the trails in the Chisos Basin and Chisos Mountains are very well established. There are no cairns, nor are they necessary.
If you do the outer mountain loop, the trails (Juniper / Dodson / Blue Creek) are also well established, maybe not quite as much as the Chisos, but with the few cairns they have, you won't get lost.
Now if you decide to take a trail like the Smoky Creek Trail towards the Mule Ears, it will involve route finding. It will be harder than the Needles in Canyonlands. At least in Canyonlands, the cairns are just atop rocks so you can see them. The cairns in Big Bend can be much bigger but they can be overgrown by plants. You will spend a lot of time looking for them in certain areas. If you're in a wash, you should make sure to see if the trail comes out of the wash by constantly scanning for cairns.
On the Smoky Creek trail, I would not rely on the cairns alone but do some dead reckoning as well using a detailed topo. Or you could use a GPS. I would imagine the trail that starts near Fresno Creek and goes by the Elephant Tusk is similar to Smoky Creek.
I watched a video a couple of guys made (I think back in 2019..not sure) while backpacking in Big Bend. They were apparently in some of the more remote areas and the trails were completely overgrown with brush and they really had to hunt for the trail and backtrack a couple of times to find it again. I'm planning a trip to Big Bend early next year. I won't be getting really deep into the park but will certainly have a GPS solution of some variety, either a mobile phone app with maps or a dedicated GPS device.