subjunctive or conditional?

[hela]

Dear teachers,

Are both forms equivalent here or is there a nuance between them?

1) I wish I were / could be you.
2) I wish I were / could be as fast as I used to be.
3) I wish children switched / would switch off the TV and studied / study more.

Many thanks,
Hela

[Tdol]

I think the modal form gives more emphasis.