Note heads and note timing
Soo if you right click the staff staff/part properties/advanced styles/noteheads and you apply akin or some other note heads and then you select a note and go to properties or whatever its called for a single note you cannot apply an "x" notehead if you want it spoken. Also, when you flip up eighth and faster notes into another note, two eighth notes will look like a sixteenth note.
Comments
Select the note you want to make an "x". in the Properties tab, scroll down to and select "show more". In "Notehead scheme" select "Normal". Then you can change your notehead to "x".
No idea what you mean in the second part.