Please share me config for 270 and 280x.
270 run 1mh it right ?
280x all HW

not really going to matter just increase intensity to you get hardware errors or it over heats then turn it down some..
there is no special tricks or configs needed pretty much stock default settings will get you the same as hardcore overclocking.
don't worry about it just get mining

edit here is my conf file i used with sgminer for my recently sold Radeon 7950..
which should be pretty close for a R280 or R270.
* adjust the shader count setting !
{
"pools" : [
{
"url" : "stratum+tcp://us-east1.jackpotcoin.miningpoolhub.com:20484",
"user" : "aaaa.1",
"pass" : "x"
},
{
"url" : "localhost:15372",
"user" : "user",
"pass" : "pass"
},
{
"url" : "stratum+tcp://www.hashharder.com:9958",
"user" : "aaaaaaaa",
"pass" : "x"
},
{
"url" : "stratum+tcp://jpc.cloudminers.net:3338",
"user" : "aaaaaaa.1",
"pass" : "x"
}
]
,
"intensity" : "18",
"vectors" : "1",
"worksize" : "256",
"lookup-gap" : "2",
"thread-concurrency" : "0",
"shaders" : "1792",
"gpu-engine" : "1060",
"gpu-fan" : "60",
"gpu-memclock" : "1564",
"gpu-memdiff" : "0",
"gpu-powertune" : "0",
"gpu-vddc" : "0.000",
"temp-cutoff" : "95",
"temp-overheat" : "85",
"temp-target" : "75",
"api-mcast-port" : "4028",
"api-port" : "4028",
"no-submit-stale" : true,
"expiry" : "120",
"gpu-dyninterval" : "7",
"gpu-platform" : "0",
"gpu-threads" : "2",
"hotplug" : "5",
"log" : "5",
"no-pool-disable" : true,
"queue" : "1",
"scan-time" : "15",
"temp-hysteresis" : "3",
"shares" : "0",
"kernel-path" : "/usr/local/bin"
}