Kh4L

On the other hand, nlohmann/json has a cleaner and more Python-like API, so if you don't care about performance that much, I'd say it's the way to go

We used to use. We first micro-benchmarked all those and we found that Tencent/rapidjson was more than 100% faster than nlohmann/json :)

Our primary use is to parse http://cocodataset.org/ metadata files and RapidJson is 100% faster.