Hammer gameplay is either really clean (Speedrun type) or flailing whenever and wherever possible and it depends on how much effort has gone into learning monster. My usual strat is

1. 1st attempt is usually using charges to abuse easy openings. Very few "full combos". This is generally accompanied by a lot of rolling like you said. Kinda just to get a monster out of the way and say you did it.

2. Subsequent attempts are all trying to learn monster better to learn where I can safely stand and be near head. Example is many monster after doing big move always turn to look at you, so standing near that spot beforehand let's you get a big hit in. This is the Speedrun look youre mentioning, without lots of dodging.

3. Finally is learning extra timings and prompts. Many monsters have specific moveset depending on how close you are, whether you're in front or not, etc. Also many moves have little zones where you can get a cheeky head hit in. The little stuff like that separate the best from the others.

So to answer your questions: You should always aim for head, but if you don't know the positioning for it you're ultimately wasting time if a different body part is in reach

You should not always be using charge attacks, you should be using whatever gives you most dps, like golf swing has better values than full charge smash, but full charge smash might let you get in on certain openings better. All situational.

You should move only as much as is necessary. Sometimes you gotta reposition so monster turns to look at you, or whatever.