A couple things about RAM:
1) RAM will only work at the same speed together. If you've got 1 set which can only get to 2666, buying a set of 3000 will only work up to 2666, so you're wasting money essentially (vs buying a 2nd 2666 kit). Also, RAM is very susceptible to compatibility issues at the best of time, even more so on Ryzen systems, and using 4 sticks of dual channel rather than quad channel (two kits of 2 vs 1 kit of 4 sticks) can be finicky to say the least.
2) More RAM barely helps for gaming past 16GB atm considering the massive extra cost. Much better to spend the money on a better CPU cooler, storage, monitor, whatever else you're looking to upgrade. If you're video encoding or 3D rendering, by all means more RAM will make a big difference, otherwise I'd stick to 16GB.
3) Overclocking RAM is only easy if you're just enabling XMP profiles, while it's technically overclocking it's also not really (as in it's tested and sold to do 3200 for example, it's not about pushing limits per se). If you get into actually pushing past what it's sold for and messing with sub timings then it's often complicated and frustrating, will involve clearing CMOS a lot. You can get a lot out of it, but up to you if the effort's worth it.
Faster RAM is only financially sensible up to about 3200, beyond that its very much diminishing returns.