From a mechanical standpoint, this is neither terribly synergistic nor non-synergistic; you can set things so you just care about Strength and Charisma pretty easily and work from there, but because the classes don’t have features (like spell slot progression) that feed directly into each other, you’ll have to make some decisions about the tradeoffs you’re willing to accept. Flavor-wise, it’s more complicated. If you’re familiar with the pop culture influences of the elementalist class, there’s certainly no shortage of elementalists with strong ideals to be found if one looks even a little bit, and fighting spellcasters focused on elemental magic are hardly unheard of either. There is a certain underlying current of mysticism to both, but expect your archetype features to do some heavier-than-normal lifting in the flavor department. More levels of herald give you a standard idealogically-powered magical warrior type, who has a connection to one or more of the elements. More levels in elementalist gives you an elemental mage with a streak of idealism. A more even distribution balances martial skill and elemental magic more evenly and probably leans into the shared mystical side. [[Synergy Feats for Multiclassers#Elementalist w/ Herald|Elementalist-Herald chains and ideas]]