Your questions are very arguable. There are very many factors to the designs of devices and connectivity standards. Of course, standards aren't very standard when it comes to real world application because every device is different in its own way as is every computer and connection.
Suffice to say that Thunderbolt 2 is perfectly adequate and fast enough for the functions and features of the Quantum.
Secondly, Thunderbolt 3 devices may not be that common as of yet. Things change fast and then change again. Nature of technology.
Lastly, yes. As Thunderbolt is a Apple and Intel standard, you can most definitely use a Mac computer running Windows with Bootcamp. It would work extremely well.
You may also find this website informative regarding Thunderbolt technology.