syntax explanation needed

There have been many threads that required a re-arrangement of the input
record.  The first proposal was '$1 = $1'

Followups pointed out the the line won't print if $1 = "" or $1 == 0, so
a fix to that was '{$1 = $1}1'

Now I can explain that, I said to myself; since } ends a line, the above
is equivalent to

'   {$1 = $1}
1'

The first action line rearranges the input line, the second expression
is always true, so now we print the rearranged line.

Kenny countered the solution of '{$1 = $1}1' with '($1 = $1)1'.  Now
that I'm not sure I understand.

What does 'expr expr expr' mean?
When is 'expr expr expr' the same as 'expr || expr || expr' ?

what does '($1 = $1)1' do? and why is it better than '{$1 = $1}1' ?

--
Regards,

---Robert