Ktor: Difference between engines

Hello, what is the current situation with the engines? As I see, the documentation hasn’t changed much and CIO still “supports only HTTP/1.x for now.” I have issues using io.ktor:ktor-client-logging with it because it demands Android 26+ SDK and I need to use 21. As I understood, CIO is the only engine supports multiple async requests with coroutines, right? But most of the time it comes with runBlocking for me, so what should I use for Android and Kotlin Multiplatform Mobile here? And how can I add logging for Ktor easily?