Uncertainty principle for pairs $x$ and $p$ or $E$ and $t$ data written for a physical particle has nothing to do with virtual pair production.

The "presence of higher states" in a given state has a limited and certain meaning and is not due to fluctuations.

Let us consider an **exact** ground state $\psi_0$. It is often unknown as analytical formula. It is the searched by the perturbation theory and is obtained in a spectral form like this one:

$$\psi_0=e^{-iE_0 t/\hbar}\sum_{n\ge 0}C_{0n}\psi_n^{(0)}\quad (1)$$

This spectral decomposition is **not** a quantum mechanical superposition of states. All higher **approximate** states $\psi_n^{(0)},\: n>0$ are non observable in the exact state $\psi_n$; they are just dumb numbers to correct inexact value $\psi_0^{(0)}$ to get the exact one, the latter being still the ground state. No experiment can find an excited state, exact or approximate, in the ground state (vacuum is a ground state). But in the formula the approximate states are present. This leads to confusion that in the ground state one may "find" higher states for short period due to uncertainty relationship. Note, the spectral expansions like (1) for other exact states are involved in real calculations where exist exact observable states $\psi_n$ which bring their own $\psi_n^{0}$ because of being expanded in the spectral series too.

No, in any particular state $\psi_n$ there are no higher observable states, it should be clear. It is a state with a certain energy an nothing else can be found in it.

The only observable state in a state $\Psi$ are those that are involved in the superposition of exact states with their own energetic exponentials:

$$\Psi=\sum_nA_n\psi_n e^{-iE_n t/\hbar}\quad (2)$$

Often some higher states are forbidden in this superposition by the energy conservation law valid, for example, for collisions.