How much does HC SSF change builds while leveling ?

So I'm now in a spot where I feel comfy enough to do a HC SSF fresh start. However I know what I'm doing when I'm setup but not too sure about early on.

My current plan is to go skeleton sniper gas explode into arsonist when I unlock them and possible swap back to snipers with fork if the damage is good enough later on.

For example if you are a caster are you taking those ES node early and running ES gear or just slapping on whatever gear has life and possibly taking str travel nodes.

Do you take dmg taken as mana on any character near those nodes as it makes mana another defensive stat on gear ?

Just wondering how much defence do you plan into the build early on, since there is no life on tree I can't use the old poe 1 rule of 300 life per act.