Small Optimization Question

My response would be, does it actually make it look/behave any better? In other words, when considering one object, go for what looks best. When considering a large amount of objects, compromise. So for your example, does disabling shadows make it look any better, and does having collisions disabled become confusing when walking over/shooting at it?

Disabling casting shadows won't affect performance at all, however disabling recieving shadows will give an unnoticeable performance increase. It may speed up the compile, but honestly, it's not worth doing.

I can't say for collisions, but i'd assume you'd save a miniscule amount of CPU by disabling them. It's really not worth worrying about.

prop_dynamic has static shadows that only affect the compile, dynamic props however have dynamic shadows. Dynamic shadows sometimes can improve the speed. Its often not that much though. but on big areas it can have some effect.

Collisions of complex objects are better to be disabled and then remade with nodraw brushes. In that case it would be usefull. however, doorway collisions realy arent any use to disable as it are such low detailed models. Same with small rocks. Its rare that it has any use (for example the badlands spiral rock usualy is better to redo the collisions for).

Its usualy better to use hint brushes or areaportals for improving the fps. Those will have the biggest effect.

lighting will only ever affect compile time, file size and sometimes the cache. Dynamic objects are so few and far between they're best to leave with lighting anyway.

Dynamic shadows usually look pretty cheap anyway. I would disable them on, say, color-changing CONTROL POINT signs for that reason alone. Doesn't disabling receiving shadows make objects fullbright?

See valve maps.