Make appendix chapter title simple

Question

I am using a fancy chapter title for normal chapters, but i want chapters in appendix to look different

\documentclass{report}
\usepackage{titletoc}
\usepackage{tocloft}
\usepackage[pagestyles, outermarks, newparttoc]{titlesec}
\usepackage[title]{appendix}
\makeatletter
\titleformat{\chapter}[frame]
{\normalfont}{\filright\enspace \@chapapp~\thechapter\enspace}
{20pt}{\Huge\bfseries\filcenter}%20pt the small line that close the box
\titlespacing*{\chapter}
{0pt}{-35pt}{0pt}
\makeatother
\begin{document}
    \chapter{Appedix testing}
\begin{appendices}
\chapter{Appendix A}
\section{subappendix}
\chapter{Appendix B}
\end{appendices}
\end{document}

Answer 1

Simply change the titleformat at the point in your document where you want to change it:

\documentclass{report}
\usepackage[pagestyles, outermarks, newparttoc]{titlesec}
\usepackage[title]{appendix}

\makeatletter
    \titleformat{\chapter}[frame]
        {\normalfont}{\filright\enspace \@chapapp~\thechapter\enspace}
        {20pt}{\Huge\bfseries\filcenter}
    \titlespacing*{\chapter}
        {0pt}{-35pt}{0pt}
\makeatother

\begin{document}
    \chapter{Appendix testing}
    
    \begin{appendices}
        \makeatletter
            \titleformat{\chapter}{\Large\bfseries}{\@chapapp~\thechapter:}{.5em}{}
        \makeatother
        \chapter{Theory}
        \section{subappendix}
        \chapter{Appendix B}
    \end{appendices}
\end{document}