'that which is (not)'

It seems that in the Sophist 'that which is' implies 'being', but 'that which is not' does not imply 'non-being', because as Parmenides says, non-being cannot be known, understood, discussed, etc., and rather 'that which is not' seems to imply 'non-form' or 'false-form' (i.e. non or false beauty). I find this interesting. Though perhaps 'that which is' actually implies 'form', more than 'being', if the two can be separate; in which case it makes more sense to use the terms 'that which is' and 'that which is not' in the same context. But what if 'that which is not' implies becoming (and 'that which is', being)?

'that which is' 'that which is not'
1. being non-being
2. form non-form
3. being becoming

Can these mix and match? I think these are merely different ways for describing the same multi-faceted concepts, depending on perception and the context in which it is discussed. Although thinking about the context in which 'that which is not' is used in Sophist, it implies non-form as in something lacking a specific form, but not necessarily a copy of a form, in the process of becoming form. But in another instance, it implies false form (the false appearance of a true form?), which brings back in the notion of non-form implying a copy of a form. But is non or false beauty or justice in a state of becoming (true) beauty or justice?