CURLpp: TLS Handshake Error
cURLpp is just a wrapper over libcURL, it doesn't dictate which SSL implementation libcURL uses.
Am not exactly sure how you've come to the when I switch to CURLpp, it uses gnuTLS, instead of openSSL conclusion but I suspect that you have multiple libcurl.so installed, the one curl uses and another that your app is using (via cURLpp).
As a side note, the TLS fatal alert ... received (mentioned in the linked question) was probably a result of a misconfiguration on the server side (invalid servername TLS extension, failure to negotiate ciphers, etc).