Health and stamina bars show what each fighter can still recover to: the hatched end is gone. Spending stamina wears its max down; head shots lower the health max. Staying out of trouble brings health back, and the break between rounds restores part of both.
Guard and head movement are held, not tapped, and blend freely. A guard in the right zone blocks; raised just before impact it parries. Head movement only counts as far as your head has actually moved off the strike's line: halfway is a graze, all the way is a clean miss and a fast, heavy counter. Leaning the wrong way walks you into it.
Footwork matters too. Each strike hits hardest a little inside its full reach; reaching or jammed loses power. Step in and punch off the planted lead foot for more. Circle (↑ ↓) and your opponent needs a moment to turn: strikes from that angle land harder and slip past blocks. Circling to your right puts your lead foot outside theirs, which lines up your right hand and takes you away from theirs.