True but you will rarely reach 300Mb on that LTE link.

That's not a LTE device. I currently get ~ 160MBit/sec on the wireless interface.
Even on LTE Cat6 or higher devices, 200MBit/sec should be achievable.

According to products specs of LHG XL HP5(and some other Mikrotik products), The max data rate on wireless port is 300Mbits/sec, but the Ethernet port is a 10/100MBits/sec one. Doesn't that make the Ethernet port a bottleneck? Am I missing something?

Thanks in advance!