It is difficult to do any assessment over the internet.

If the timbers are not charred, it means they were not exposed to fire, otherwise they would be charred. The charring occurs at around 300°C.

The checking and twisting is most likely result of severe drying during the fire in the house. Uncontrolled drying conditions can cause great checks and twist/warp. If the timber contains pith it can be even worse.

Exposure of wood to elevated temperatures for some period of time causes the chemical changes in the wood accompanied by decrease in strength. There were several articles published on this subject.

Regarding the appearance damage, I can not comment on that. But some people like those large checks and aged wood look. I guess it is matter of preference. If you need to get more info, email me dalibor@van.forintek.ca or call 604-222-5658

Dalibor