I just bought a new 4K TV, so I’ve done a lot of research recently. I don’t have personal experience with TCL, but I can share general conclusions from my research.
The main selling points of the brand are low price and great user interface for the smart features. They review well in general, and often take the prize for “best budget model”. The picture quality is on par with the lowest tier panels from all the major brands. It’s not bad, but won’t have the brightest colors, deepest blacks, or most accurate colors. Most viewers in most environments will not see anything wrong with it.
I’m no expert, but I don’t believe there is any “certification” for HDR10. HDR10 is in the signal or it isn’t, and the TV can process it or it can’t - much like audio codecs. The quality of the HDR10 picture will vary from panel to panel. I don’t think I came across a single 4K TV that could not handle HDR10 content.
In any case, don’t take my word for it! Try this.
https://www.rtings.com/tv/reviews/tcl/s-series-4k-2017-s405