Thanks for the suggestion.
Moca will help the Master room and big common room to get near 1Gbps speed since they have SCV cable TV point (HDB is 1998). But not on the small common room which does not have the cable TV point.
One thing against the Moca is that they are not certified by IMDA. But it is probably because IMDA is behind the curve in this aspect or they prefer structure Ethernet wiring. So this is a moot point and not really a big concern for me.
The main problem is that the coaxial cable may not be well laid out and quanlity may not be good -- last time I got problems with over the air TV before I switched to SingTel TV in Feb 2011.
For now I am happy with the Power Line adapters. We do not really do any high bandwidth activities at home (at most 1080p streaming and NAS backup of phone photos to NAS). I am getting above 200Mbps wifi (up to 400Mbps) in my living room and big common room, above 100Mbps wifi speed in master room and small common room. These are more than enough for the family members.
But next year I may get WiFi 6 equipment, like AX3000 or higher spec router to replace the aging WRT1900AC router (early 2014 to now). Then I may want to get better Mesh as well.