How can i get the best speed out of my 3 WAN's

hi there, so let me get into my current setup first
i have a balance 20,
WAN 1: a note 4 android mobile with an LTE connection
WAN 2: a 4g router with an LTE connection
WAN 3: low 6mbps speed but stable unlimited ADSL line
Lan out: into a portalwifi router

now here is my problem, no matter how i tried to play around with the policies (lowest latency, load balanced…etc) i am unable to always get the fastest connection when testing (the LTE speeds depends on the time so its not always A > B scenario)

so my questions are:
1- if i enabled VPN on my router level, will that achive anything in terms of getting the best speed?
2- with my model/config can peplink vpn solutions help in anyway
3- whats the best policy you guys recommend to get a stable high speed connection with my setup ?

thanks in advanced