Please can you check if the interface are correctly configured?
They look fine to me. But the real question is, does it work? If you can answer that question, then you can answer your own question yourself ("teach a man to fish...")! You don't need validation from me. If it works, it is correctly configured. If it doesn't work, then it is not. Elementary logic.
If it doesn't work, then we can start to examine the "why".
I also Unchecked "Change TCP MSS", is it correct?
Yes, that's fine, although I suspect it would work fine even with it checked. "Change TCP MSS" takes into account the MTU (subtracting 40 from it, which is the total size of the IP + TCP headers together). It doesn't just blindly make a rule that forces the MSS to some predefined constant value. So if you have "Change TCP MSS" checked on a PPP server which is set for 1500 MTU/MRU, then that checkbox would craft a set of mangle rules to lower the MSS to 1460 if the TCP traffic it is forwarding is advertising an MSS higher than that. But it will never be higher than that for computers with 1500 MTUs that are behind the router, because those computer will be negotiating/advertising a 1460 MSS anyway! So no harm done.
And last, is there a method to see if fragmentation appen in the way and not only in the test router in which I ping google.it size=1500 do-not-fragment ?
Not sure what you want. If you can ping down the tunnel with 1500-byte sized IP packets and DF bit set, and you get responses back, then no IP fragmentation is occurring. If you want further proof above and beyond that, then hook a computer up to the PPPoE client router, install Wireshark to it, and do a packet capture while you try to do something on the internet (e.g., visit
www.mikrotik.com in a web browser).
-- Nathan