There’s good arguments for both. Ur coming from VDJ and apparently ur open to other software.
Twitch is a nicely integrated no hassle package, a nice advantage in ur case IMO that it works well with Traktor out of the box, but also comes with a full license of Itch (soon to be Serato DJ). It only has one effect unit which could bug u in Traktor, but there’s the pads for some midifighter-esque effects mappings, so that shouldn’t keep you off – apparently ur willing to do some mapping.
The X1 is nice (have owned one, also the Twitch, never used K2), but it IMO only makes real sense with a mixer. Idc how you map it, the K2 is not a mixer. It’s another version of an X1 basically.
Twitch works great out of the box, great value for money, gives u choice of software.
X1 + K2 have more mappable controls between them (don’t see the need for that in what you say you do though). More effort needed mapping.
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