Are the functions on WeDJ for iPhone the same as those on WeDJ for iPad /WeDJ for iPhone?

No. The functions on WeDJ for iPad and WeDJ for iPhone are different from those on WeDJ for iPhone. Visit the following product pages for details.

WeDJ for iPad
https://www.pioneerdj.com/en/product/software/wedj-for-ipad/dj-app/overview/
WeDJ for iPhone
https://www.pioneerdj.com/en/product/software/wedj-for-iphone/dj-app/overview/