How to bound a running time equation?
Every function is big $\Theta,\Omega,O$ of itself, so you can already put your result in big $\Theta,\Omega,O$ notation. Using $4^{\log_4 (2n^2)} = 2n^2 = \Theta(n^2)$, you can also write $T(n) = \Theta(n^2)$; I'll leave you the details.