My model-specific camera l-plates are from various PRC manufacturers, and I decide based on whether I like the design and features. Latest is a Nikon Zfc plate from
Neewer. Despite modest price, it's nicely finished and works perfectly. Have previously used products from a high-end USA company, and these were also good quality, but they didn't always have the products I wanted, and I was never fond of their reliance on hex screws.
Tripod heads / clamps: Arca-Swiss, Joby, Vanguard, Hejnar and ..? There are lots of decent choices these days, and a (much) higher price is no guarantee that you'll be more satisfied with a product.