If you are not planning on overclocking and just want a fast and stable PC without spending too much money then I recommend 2x16GB DDR4-3600 and anything like CL16-18-18, CL16-16-16, or even CL18-22-22. This is because you won't see any special difference and the top DDR4 may cost twice as much as these cheaper series.
There are so many RAM brands and series that is hard to make any clear RAM list. I had no problems with HyperX, Ballistix, G.Skill but also brands like Patriot, Silicon Power, or Team Group. I recommend picking something that looks good and isn't overpriced. Every respectable brand gives a lifetime warranty so this isn't an issue. Being on the compatibility list of your motherboard is generally a good idea.
I wouldn't buy 16GB RAM if you are playing new games and use a web browser and maybe other software in the background. As far as 16GB is enough then you can go close to its limit while running multiple applications and many tabs in the web browser.
Another thing is the investment. In a year will be DDR5 so also new processors, new RAM, and new chipsets. If you are planning on keeping the PC for 3-5 years then get 32GB. If you are going to replace it in a year then maybe don't waste money on a higher CPU and more RAM.
5600X and 5800X give about the same performance in 97% of games. What's left is usually used in reviews for comparison
In new games, what matters more is a graphics card. Investing in a better graphics card is a better idea than a CPU with more cores. This also depends on prices and your budget.