You are forgetting yet another option which is widespread and common practice among serious C++ developers, which is to use the Compiler Explorer to see how the code directly translates into machine instructions. It is almost normal to always have this open next to your IDE if you care about performance.
Note that most people who use Compiler Explorer don't actually know assembly that well, but you don't need to know it to see what is happening at a basic level, which usually suffices.
However, it is not necessary to care so much about performance in most cases. The language is generally fast compared to other languages, even if you don't try to make it fast -- the compilers and the language spec usually have that outcome. But when you really want to squeeze out the most efficient code, Compiler Explorer is the way most people do it.
Note that most people who use Compiler Explorer don't actually know assembly that well, but you don't need to know it to see what is happening at a basic level, which usually suffices.
However, it is not necessary to care so much about performance in most cases. The language is generally fast compared to other languages, even if you don't try to make it fast -- the compilers and the language spec usually have that outcome. But when you really want to squeeze out the most efficient code, Compiler Explorer is the way most people do it.