but witch hazel is an astringent. I wouldn't classify it strictly as a post shave product as it can be used anytime. It will stop weepers and cleanse the skin. I believe it is also an anti-oxidant. you can use it for other things as well such as treating bug bites. It is also used to treat acne. so general use of this stuff daily is really good for you.
clubman is an aftershave splash. it contains alcohol so it will likely burn/sting some. speaking for myself it doesn't provide any moisturizer and drys my skin......probably the alcohol.
nieva is an aftershave balm. it will sooth your skin and prevent razor burn. in my experience it also provides some moisturizing.
around here there are a lot of people mix the products you mention together. such as cleanse the face with witch hazel then apply the clubman or nieva or any other AS or ASB.
WH will close pores and have an antiseptic effect. Clubman will add another antiseptic effect plus scent. The balm will further condition the skin and will hydrate as well.
I'm the furthest thing from an expert, but this is the general idea I have about the properties of these products.
Pores do not open and close as they have no muscles. This is a myth.
WH is an astringent and supposedly has many beneficial properties for your skin.
Clubman has alcohol in it so is an antiseptic and might have moisturizers in it as well, I dunno, I've never used it.
Nivea is an aftershave and moisturizes your face and soothes razorburn.