i'm running v5.1 on x64 with XTC. As XTC vst version is quite old (from the nineties), not all daws run these plugs, but some do. For example, Samplitude 11, Live! 8, older versions of Cubase (haven't tried new though)... others just scan them but not initialize.
i'm happy with it. it can't 'render', must do realtime, but it works.
I recently found this in an old SOS review of the old Creamware XTC mode - about 'Direct Play'. Its basically what I'm doing anyway in using the XITE-1D as an external MIDI instrument & routing back via ADAT. But useful to know for those contemplating a similar use case assuming a modern incarnation will also have 'Direct Play'.
"As mentioned in the box on latency earlier in this article, playing a SCOPE instrument so the output doesn't pass through an ASIO driver's buffers normally allows that instrument to be played virtually latency free. However, running a SCOPE instrument in XTC mode as a VST Instrument causes that instrument to be affected by the overall ASIO latency. Fortunately, Creamware have come up with a particularly neat way of overcoming this problem by implementing a feature called Direct Play (which, by the way, isn't related to Microsoft's DirectX technologies). What Direct Play enables you to do is route the output of all the SFP instruments (when they're used in XTC mode) directly to one of the hardware outputs on the card, enabling them to be played as if they were running as stand-alone instruments, rather than VST Instruments."