Thank Yous

I think it's perfectly fine to thank them verbally and would probably be awkward if you just didn't mention the gift that they sent. If I was the sender, I would wonder if you even received it.

I would say it doesn’t hurt to thank them before if you see them before you send out their thank you note.

I think it would be perfectly normal to thank someone in conservation, also. But definitely still send them a handwritten thank-you, which it already sounds like you're planning on doing!

You can do both!

I think that's totally fine to thank in person in addition to the card!

A hand written note is customary for wedding gifts

Yes, an additional thank you, unless you are in a situation where someone who might have considered herself close enough, but was not invited, is present. Then you save it for another time. You can say it in front of someone who would never ever have been invited, or a stranger. Because talking about it won't make that person feel bad she did not come.