It would be great to use VS2017 for the N2+, but I think I have it in a usable state, here is where I'm at:
I cannot get the fancy looking Netduino Deploy 2.0.3-beta tool to talk to the N2+ again, it consistently tells me to restart the application with the N2+ in bootloader mode..... not sure why it lost the ability to talk to the N2+, but the MFDeploy tool seems to have the same/similar capabilities.
I uninstalled the WinUSB driver, uninstalled the SDK, put the N2+ in DFU mode and reinstalled the SDK - this restored the original STM USB driver - this caused the DfuSe demo application to see the N2+ again.
I used the "Dfu File manager" to create a .dfu file from the .s19 formatted firmware v.126.96.36.199 included in one of the tools you pointed me to. Then I used DfuSe to flash the .dfu file.
I can't figure out what to do with the ER_CONFIG.S19 and ER_FLASH.S19, the MFDeploy tool you mentioned has an option to deploy an "image file" but it has to be a .HEX or .NMF formatted file - I tried to use DFU File manager tool to convert the .S19 files to .HEX but the MFDeploy tool couldn't read them.
Thank you so much for all the help