It is found that lagging in text input when using virtual whatever sometime it won't happen. It seems that it still lags after restarting the ZenFone 9. Scan and memory clean are also performed.
based on my experiences, I also have the same problem with lagging in text input when using a virtual keyboard after updating the firmware to .142 (new initial firmware Android 13 updates). Sometimes it won't happen the lag but it getting annoying for daily usage
so I downgraded my firmware to .38 (the last firmware Android 12 updates) and the problem does not happen again
Sadly, all old firmware on Asus web was gone forever without an official announcement to the user.