Your questions seem to me to be along the lines of "what effects are better?" which is purely subjective and not allowed, but I'll give you a quick rundown of the interactions.
Ignoring the effect cimetidine might have on absorption of chemicals due to acid levels in the GI tract, it limits the hepatic metabolism of many enzymes. This means that taking it will make your clonazepam and hydrocodone last longer, and if they were taken orally increase the total amount getting into your system as well. The same inhibition of the enzymes will somewhat limit tramadol from being converted to O-desmethyltramadol as quickly.
The antihistamine diphenhydramine is hypnotic, will prevent opiate itch, and also has an inhibitory effect on a liver enzyme. Benedryl and Nyquil are both brand names and though Benedryl often contains only diphenhydramine (at least around ontario) I'm pretty sure Nyquil has a bunch of different active ingredients and you really should try and be more specific.
