Is it the Stylus or the App. That provides Palm Rejection on IPad?

I am unable to write (hand-written notes) properly on my Ipad screen without Palm Rejection. I found out that, there are stylus-es and apps pairing which gives Palm Rejection (its not providing a palm rejection pane but the entire screen recognizes only the stylus and no other touches), but those are note taking apps and not screencast apps.
Is it the Stylus or the App. That provides Palm Rejection? Can I use the above mentioned Stylus with Screenchomp, etc. To create screencast? Can you please. Suggest how can i create screencast with palm rejection?

Also, can you from your experience, please. Let me know if writing on Ipad screen be easy or very difficult (as compared to wacom tab)?
I am planning to create educational screencasts.
Please. Suggest good stylus and/or apps for this purpose.

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