Directional chains are easy enough to spot --- they are asymmetrical, obviously so, either top/bottom (as is a Connex link), or with different inner and outer plates. If you can't see any asymmetry then the chain isn't directional.
There's a sort of exception on pinned chains such as Shimano and Campagnolo because they often specify the position (back or front end of outer plate) and direction of press of the closure pin. So cutting the chain leaving an inner link at one end and outer at the other sets a drive direction. This doesn't apply to chains closed with a connecting link.
Count me among those who consider links to wear with the chains, and so the same link should stay married to the same chain forever (except in an emergency). As to the various widths, if it fits and is the right width, up to a fraction of a mm wider, it's fine. Too narrow binds and stresses the link, so make sure it's a nice easy slip fit when closing.
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