RB750/750G - Dual WAN Load Balancing
Barely after few days of using, I was forced to terminate P1 Fiber, read HERE to see how Pui-1 can be !! 
For time being will stop this configuration & testing until I find another reliable ISP ....
Recently I applied the P1 Fiber ForBiz package (what a bloody journey!) for my home office, I'm still keeping the existing UniFi as backup, so I start venturing into the dual WAN setup using the RB750 ....
My plan is to connect both UniFi (VIP5) & P1 (Biz5) as follows diagram:
As usual, after Googling, researching & reading through, I'm blur like sotong ... 
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Basically it seem like most people will recommend to use either PCC or NTH method.
Before I continue to test out, I renamed the following port name for easier reading.
Setup & tested both PCC & NTH (refer below links), still playing/testing around .....