I'm confused what you mean by the subscriber is not accessible? Replication runs continuously, so is the subscriber never accessible? Or do you have scheduled subscription pull/push?

I haven't seen SQL Server not work during these times. When it's not accessible, do you mean you cannot connect? Or some stored procedures have long runtimes? Can you narrow down more what's happening?

When transaction replication runs, it doesn't necessarily stop access to your data. It runs log records back against your database, just like another user that's connected to the server.