That rattle, in neutral, with the clutch pedal out, is called roll-over rattle. It will only happen when the transaxle fluid is hot; it is totally harmless. By comparison, you should hear how rattly a diesel tractor is, with the thirteen or eighteen speed Eaton transmission!
If, by comparison, it makes noise when the clutch pedal is pushed-in, then it may very well be the throwout bearing. That is a cause for concern, 'cause it's so much of a "beach" to get to!
Don't worry about roll-over rattle. And notably do not change transfluid to attempt to quiet it down; trans fluid viscosity is very carefully chosen by the designers, to ensure that lubrication of the needle roller bearings (in the case of the MTX75 transaxle) get lubricated properly! Also, the fluid properties figure big-time into the behavior of the synchronizers.