The Proxmark is a good tool, but it’s not the most friendly device for simple reading/writing functions. For example, if you just want to program your vCard to the flexNT, then an NFC phone will be just fine for that.
The locking problem is not a problem with any of the readers, it’s purely an issue of having a poor coupling at a critical moment during the write process. Check this thread for more info on that.
VivoKey won’t necessarily benefit from the proxmark… at least not unless you are going to try to do some security research with it.