Welcome to the forum Pradeep!
I believe that it would be tough for you to use the newer Korgs with the touch screen. Stick with a PA80 or PA50SD on the Korgs, they still sound good to my ears.

If your heart is set on Pa500 ORT, what you're asking is doable but your best bet (for many of us) would be to set up your splits, voice changes, etc. in advance as user programs, and then use a foot pedal or assignable switch on the panel to step through them.

Re: Yamaha... personally I wasn't that impressed with the Tyros 1 when it came out. But the PSR-3000, PSR-S900, S710, S910, Tyros 2, 3, 4 all sound great and you will probably find them easier to navigate. I think the S710 comes in an Oriental model too.

Did you also listen to Ketron? They are a top-shelf arranger, they have Asian models, and I believe they do not use touch screen.
Hope this helps,
Ted