I don’t have a lot of thoughts on the other questions, but swag is something I already have general thoughts on.
I’m really not into wearables for swag. T-shirts and hats especially are items that I always give away, I just will not use them. If I like a vendor I definitely will talk all about them to other folks, I don’t need to become a walking advertisement :)
I’d be more interested in stuff that have some sort of utility, like sticky notes, pens, flashlights, usb cables, etc. Stuff that is nicer quality (I know this might mean less to give away, but I will also just throw out flimsy pens or whatever if they don’t work.)
One really cool swag I got from a vendor at my last job was this really cool flashlight that the light part had a magnet in it and could be telescoped out from the body.