If I equip stardrake Icon and/or wardrum to my saurus unit Is it gonna be less attack for that unit because they lose thier halberd,club&spear
No, it is assumed that they also have the same weapons in addition to their drums or pole. It is in the FAQ.
Yep, it's the same as the old "full command" in WFB: they fight as they have the same equipment of basic troops.