The 3 Republican presidents were lumped together as identical. Is it right to say this or were there personal or political differences?Presidents...

I am assuming that you are asking about the three
Republican presidents of the 1920s.  I have edited your question
accordingly.

There were certainly major similarities
between these presidents.  The most prominent of these was that all of them were
generally pro-business.  They were all opposed to the sorts of reforms that
Progressivism had pushed.

However, they were very
different, especially in personal terms.  Harding, for example was something of a
playboy.  By contrast, Coolidge was known as "Silent Cal" and was a serious family man
(though he did enjoy dressing up as an Indian, of all things, and having his picture
taken).

Politically, Coolidge was the most laissez-faire of
the three.  Hoover, by contrast, felt that government and business should cooperate. 
Where Coolidge thought that government should stay out of the way of business, Hoover
thought the two should work together to improve the
nation.

These three presidents had common attitudes, but
they were certainly not simple copies of one another.