If the recording has dropouts where something was spoken but not captured, that can’t be corrected and needs to be fixed before recording.
Some people use limiting to deal with spikes. If there are “mouth smacks” there is an experimental De-Clicker for speech plugin.
There is Change Tempo but it does not work well for slowing down an individual word or vowel because it is not length accurate. Try Sliding Time Scale / Pitch Shift which is slower but length-accurate.
You can use any of the above effects in Chains for batch processing and effects automation but a Chain applied to the waveform on the screen can only operate on one selection at a time.
Tempo detection is hard. It usually only works (somewhat) for pop songs with strong beats. As far as I know there is no reliable way to detect tempo of speech.
Gale