Hello and welcome to VU...
I have to answers...
1) either wall wort should be fine. It's the charger that screws into your charger that matters...it should be able to handle the input from the wall wort and convert down to the 420 ma that the ego battery charges at that matters...look at the back of the actual ego charger and it should have the input/output info on the back. I've used 700 ma wallworts and 1 amp carplugs to charge ego batts without a problem...it should be fine but it doesn't hurt to check.
2) If you have a the T3s single coil tanks those are old school, I used those a long time ago and I liked them...The T3 was Kanger's first bottom coil design. Either are good for safety as long as their Kanger coils, as to which resistance to use....1.5 ohm heads with give off more vapor and drain your battery faster. 2.5 ohm heads will give off less vapor and drain the battery slower. Both heads will gunk up but the 2.5 will last a little longer if you keep your heads clean because they don't get as hot and will burn out slower if all things are equal. But remember, coil heads are massed produced and their QC isn't perfect.
