@HK.Process This became even more confusing since i tried talking to the Live Chat agent about this issue, and they said the VR400_v3 has better signal quality and  range since it uses two "Stronger Omni Direction Antennas" (aren't all Antennas Omni direction??) while VR300 "uses regular antennas"...

But then i contacted tech support through email and they reached back and said, regardless of 2 or 4 antennas, both of these models perform the same when it comes to WiFi signal quality and range...however they didn't give me any estimate as to what to expect from a single Router on 5ghz.

Based on my own research however, the best option would be getting a dual band AC1200 Router/Modem and adding WiFi extenders and make a unified dual band 2.4Ghz and 5Ghz WiFi Mesh. So the VR400_v3 would be the choice since it supports Onemesh ( which is TP link's specific brand of WiFi mesh and the VR300 does not support this feature) and then also buy 1 or 2 WiFi Range extenders like TP Link RE300 (and again surprisingly RE305 also does not support Onemesh despite being a higher model with antennas unless it's RE305_v4 which finding that is another headache so I'll just buy RE300 or RE315).