As mentioned by Norman, you will need to increase the reverb and chorus sends for the multi pads in the mixer. If that does not work, specially for the chorus, try going into multipad creator (after selecting the multipad that you want to add effects to) , navigate to step edit tab and increase the reverb and chorus sends for each of the 4 multipads.
I wanted to add effects like delay to a particular multipad, but increasing the send in the mixer did not work, so I thought this was a bug or some issue with multipads - totally frustrating. Luckily I found this thread and as one of the earlier replies said that we could add a DSP by going into step edit, I tried the same for chorus
... the multipad sounds amazing now.
Thanks for your help guys, the PSR S 970 is a total beast