The basic pay structure for 3SG is $560. At
least that's what i got. I heard some people got the 1 year
increment of $30 more but i didn't get it. This is for the
logistic/service side.
Basic for CPL is $420.
But you must take into factor the combat allowances ($100, $150
etc, varies from vocation) and all the misc stuff. A 3SG in BMTC
can get $200 more than me with all the safety hazard and lan jiao
hazard benefits. 
Lastly, no. A private will not get $20 more than recruits. However,
according to CPC, after 1 year, a private should get $20 more from
his usual $350 (but i know alot of my guys couldn't get that extra
$20 claim automatically unless they call up CPC). If he is a LCP at
that point (which most likely he is), he will move from $370 to
$390.