I’ve had a mental picture of this—it was more death by laser beam than actual fire. But actual fire from God is correct.
However, the men weren’t completely charred, but their tunics remained.
Numbers 10:4 Then Moses called Mishael and Elzaphan, the sons of Uzziel the uncle of Aaron, and said to them, “Come near, carry your brethren from [a]before the sanctuary out of the camp.” 5 So they went near and carried them by their tunics out of the camp, as Moses had said.
One more thing: these were Aaron’s cousins. Aaron was 83 or so at this time so they were likely old and gray-headed, unlike the portrayal of some of the illustrations.
God works with high precision! You've correctly spotted some of the curiosities here--your inquisitiveness is paying off. Fun, isn't it? There's just no end, once you start. God loves us paying close attention, as long as we also get the big picture. I'm finding that seeing all these images really opens my eyes to all sorts of discoveries.
Here's a linguistic one (yours are both physical). When Moses wrote this account (in the second person), why did he refer to Uzziel as "the uncle of Aaron", rather than the more fully correct "Uzziel the uncle of Aaron and Moses"?
I was sad I could only find that single image of them hauling away the corpses. But it speaks to James Tissot's greatness that he saw the importance of it. In a very brief time, for several key reasons, Tissot has become my favorite artist, by far.