Line of sight wireless are wireless which enable antenna to sends and receives a microwave signal to the ISP's antenna
By standing between the mounted antenna at client building so that the other side of the wireless connection you intend to create can be visible.
Line of Sight wireless also provide electro-magnetic radio waves that tends to be less affected by external forces leading to better connection reliability because all wireless networks excel only with true line of sight that is why it is always advisable that the antennas are mounted above the tree line, to ensure proper connections without obstacles between them since
Line of sight depend on having a clear line of sight between the antenna and the hotspot .
0.75 miles of range is a low distance for a WAN (Wide Area Network) so a point-to-point WAN tehcnology such as IP-sec or SD-WAN can be preferred. But the least expensive option would be choosing IP-sec as specified in the question.
The difference is that system on a desk top preforms all the basic tasks like file management, memory management handling input and output and controlling peripheral devices such ad disk and printers where as some smart phone work on specific hardware