Can I use a VXDIAG VCX NANO with the official Techstream software?

No

 

I have no idea why not. You need the J2534 driver DLL that comes with the Nano. That's what Techstream will want.

 

Why not use it with downloaded Techstream?

Do you have the Nano?

2 day TIS doesn't have any relation to the VXdiag Nano that I know of, unless I'm mistaken.

 

Why not try the 2 day TIS instead of asking here. Let us know what you find out so we know next time.

 

Probably because neither 2 day TIS includes Techstream, have to buy it separately.

A Professional Diagnostic TIS subscription provides the same access to the technical information library provided with the Standard subscription. A Professional Diagnostic subscription also allows use of Techstream scantool software, all available ECU calibration files, and Identifix Direct-Hit (details below). Package a Professional Diagnostic subscription with a TIS Techstream or Techstream Lite to fully enable scantool diagnostics and vehicle reprogramming capability (USA/Mexico VIN information only). For more information on scantools and vehicle reprogramming, click here.

 

In my experience, the Professional Diagnostic subscription to TIS does include the Toyota Techstream software. Note the ■ symbol for “Techstream Scantool Software” in the chart on the techinfo.toyota.com home page.

The subscriptions don’t include hardware, for which you can use a Techstream (cable and PC) or Techstream Lite (cable only) kit bought from Toyota’s distributor (I have the latter), a MongoosePro cable bought directly from Drew Technologies, or some other compatible, J2534-compliant vehicle interface module, such as the Tactrix Openport 2.0, which I’ve also used with my car.

I haven’t tried any VXDIAG products, but as @ChapmanF observes, if they provide a device driver and SAE J2534 pass-through library and implement the needed capabilities in their hardware, there’s no reason one shouldn’t work with Toyota’s software. This doesn’t fully address the concern about installing software of unknown origin, however: even if you download the Techstream software directly from Toyota, you still have to install and use a device driver and J2534 library provided by a third party.

 

I was about to post what Elektroingenieur got to first, but yes, just to echo a little bit: you can download Techstream from Toyota and save yourself any concern about the copy of it that might come with the Nano. But for it to work with the Nano, you will still have to install the driver DLL that comes with the Nano, so it's still up to you how much you want to trust what software came with it.