The Verizon M8 for Windows works out of the box on T-Mobile with a T-Mobile Nano SIM. You will get HSPA+ 21 speeds with the 850 and 900 bands and LTE (where available) on the 1900 and LTE band 13. It works very well on those frequencies.
That said, there is no way to enable the MMS settings. MMS is picture messaging. So when someone sends you a long text that is sent as 'one message' it won't come through. When someone sends you a picture message, it won't come through. If someone tries to message you a ringtone, it won't come through. Any media sent through the Messaging App will not be received.
Other than that, the out of the box VZW device will work just fine.