About half my shirts have French cuffs, and I also wear button cuffs. I have a few silk knots that I wear infrequently, but when I do it's for the reasons mentioned: lightness, less formality, and when I want a dark color. But their fairly protruding profile does not make them, to my mind, any more discreet than normal links. I think the degree of contrast in color/light-dark value or (in the case of metal) gleam between shirt, link, and jacket sleeve is more important in calibrating the effect. I most often wear unbordered mother-of-pearl disks like these:
Or gray abalone disks of the same kind, or plain flat 14k gold ovals. I tend not to wear the gold when wearing a blazer with gilt buttons, as it seems a bit much gleam in a small area. I may acquire plain sterling ovals at some point. But frankly I can't see how any of those could raise an eyebrow.
As for sources, vintage is often the best way to go. I purchased all three pair mentioned above at a small shop specializing in vintage cufflinks and necklaces in an antiques "mall" in a building somewhere in midtown Manhattan, the name of which I cannot now locate. Perhaps our member "Cufflink" would know it. The prices were not flea-market bargains, but neither were they exhorbitant. I think I paid around $40/pair for the MOP and abalone disks, and about $200 for the 14k gold ovals, which are substantial in weight (more so than the thin domed gold links so common around the turn of the 19th-20th centuries).
Good luck!