I have personally never had a case where vector gave TLE and array gave AC

Vectors usually cause TLE if you use a lot of small vectors. If you only use big vectors, there shouldn't be a big difference in performance between arrays and vectors.

It happens in this case when you pass a large vector to a function without reference, the function creates a local copy of the large vector and time is consumed in the process while arrays are passed as reference by default, so in this particular case the execution is fast with arrays. So, I personally suggest that pass vectors by reference to any function(or make them const if no change is required to be made) to avoid ambiguous TLE. Or you can declare them globaly and directly access them in your functions(which people generally do).