This is about as high-synergy as martial/ spellcasting combinations get. The classes both are slot-based and use the same ability score (Charisma) for their supernatural abilities, so you only need to worry about Strength and Charisma, and you’ll have continued spell slot advancement as well. Flavor-wise, it’s kind of what you make of it. The class fantasies of the herald and sorcerer don’t exactly conflict with one another, but neither do they particularly overlap. You’ll want to give some thought to the character’s backstory and figure out why someone with innate magical powers pursued herald training or under what circumstances a herald unlocked their innate magical abilities. A stronger emphasis on sorcerer maximizes your spellcasting, but you’re likely going to want at least 5 levels of herald so you can get your hands on Extra Attack. Going more herald basically just diversifies your spell selection at lower levels, which isn’t nothing; even just the three levels of sorcerer necessary to qualify for the synergy feat chain can give you some really strong options like shield and grease. A fairly even mix is also pretty viable, though you’ll still want 5 levels of herald for Extra Attack. [[Synergy Feats for Multiclassers#Herald w/ Sorcerer|Herald-Sorcerer chains and ideas]]