It would be different. A large number of real world applications aren't especially performance sensitive and it makes sense to have tools that prioritize other things than performance. We also see how languages that do prioritize performance can suffer in other aspects (C++ is a clear example).

I think that this is fundamental in some way. Consider arithmetic. Fixed with integers suck from an ergonomics perspective. But variable-size integers are necessarily slower. Even designing something as basic as how arithmetic will work in your language forces you to consider performance against usability.