RPM WAP 7 according to my knowledge I have mostly seen with trains originating and terminating at Chennai Only eg.
12623 TVC Mail.
12685 Mangalore Mail
12695
and also Allapuzha mail
Some...
more... trains from Coimbatore like
Kovai Express
Intercity Express towards Chennai.
Shatabdi Express ( not always)
Blue Mountain Express
Chetan Express
Coimbatore -Jaipur Express upto Chennai
Rapti Sagar Express. As Offlink
So you should know from here that trains which are originating from Chennai are most likely to get WAP 7 of RPM
for other electric locos mostly expect only ED WAP 4 or AJJ WAP 1
So according to me trains passing via Erode but not Chennai will get ED WAP 4 only.
And RPM shed will also mostly use RPM WAP 7 for Chennai to Madurai,Villupuram,Kanniyakumari and Tirunelveli route trains.
So I am picking TRAIN NO 12685 Mangalore Mail as No.1 Contender for WAP 7 RPM.
And 12601/12602 also.
For trains passing via Erode ED WAP 4
But, there is a problem with Chennai Egmore Train
This train have a Loco Change at Tiruchirapalli from Diesel to RPM WAP 4/7
So I don't think they will make a 2 loco change train. They will wait till Trichy to Erode line gets electrified by 2018 end