Is it a good idea to apply for the position of Research Assistant instead of PhD?
That way we can be paid while working towards a PhD.

Yes I agree with u

It can be a good idea, but you'll need to check that you will be able to register for a PhD. Competition for research assistant places is very high.

do you know how one can apply for such a position? and is it more competitive than applying for a PhD?

Such positions are advertised either on this site, in the press or on departmental web sites. You should not apply speculatively.