The synergy here depends at least a little bit on the wielder archetype selected. Because your wielder archetype determines your casting ability score, characters taking (for example) the Reliquarian or Torch Bearer archetypes for the wielder class will have greater synergy than the Enigmatist or Entrusted. Aside from possible ability score overlap, though, the synergy is minimal. Wielders have points-based spellcasting and druids have slot-based, the focus is also different with druids being more of a “primary spellcaster” and wielders mostly using their magic to enhance their combat prowess. Build-wise, it probably makes the most sense to pick one of those approaches as the primary one and (mostly) stick to it. Wielder levels can be a nice way to create a “lord of the wilds” type of character that has a lot of magical power but also can hold their own in a direct physical confrontation. More levels of druid will lean into magic and shapeshifting with a bit more weapon use and perhaps better armor (depending on the bonded artifact type) than a normal druid, whereas a focus on wielder will probably make a more stealthy and tricky wielder who uses their limited Wild shape capabilities for scouting and reconnaissance. An even mix, while tricky, could be an extremely versatile character, but might struggle to do anything particularly well. [[Synergy Feats for Multiclassers#Druid w/ Wielder|Druid-Wielder chains and ideas]]