cuff links

First off I have seen the real men real style video on the subject.

I have two questions, first will dull black metal cuff links clash with the steel of my watches and belt buckles? And second, what is the formality of cuff links that have a chain attaching the two sides (they weren’t covered in the video), is it the same as the ones with the swivel bar, since they both have moving parts? or is it like the shank cuff links since they can both be decorated on multiple sides?

Summer overcoat

I have a very nice overcoat that I wear during the winter. Where I live it can get too wet in the summer for a regular suit, but still be too hot for an overcoat. I’ve been reduced to taking off my jacket and wearing a windbreaker. Is there a solution?