Well maglevs are not used today exactly because of this issue - going past 600 km/h is dangerous - causes noise and turbulence affects the train too much, so it makes sense to venture in another direction, such as maglevs but in tunnels.
What's addressed in your comment? You didn't show any other alternative offering speeds like Hyperloop, in theory, could.
Not sure what you mean by your question about "which designs" - well, Hyperloop. Or do you expect me to hand you a finished project? It's just started. Even bullet trains took decades to get from proposal to project to finished.
