<<"Would taking the Glacier Express from Zermatt and following up the next day with the Bernina Express to Lugano be too much.Is it better to have a 2 night stopover and would Chur or St Moritz be a better choice? This will be in the first week in October.">>
Perhaps you missed it....Arno answered your question in your thread that more or less focused on Luzern and Zürich.
It is difficult to answer the question of "what is too much." That is a matter of personal opinion.
You can judge the time spent on the journeys by using the timetable:
Some people come to Switzerland simply to ride as many trains as possible; others enjoy the rides but want to get around on their feet, or by local transport to scenic places and spend time close up to various attractions. Some want to enjoy the mountain inns, etc. You really have to make the judgements yourself. The timetable helps by showing you times of travel and possible routes.
Often, a map is useful, too:
Arno has noted that St. Moritz has plenty to do and see, and, in my opinion has a wider range of scenic and interesting things for a tourist than does Chur. It is certainly famous for a reason. It is also heavily populated with tourists.
One thing that we have enjoyed many times near St.Moritz is to take the Funicular up to Muottas Muragl, where there is a nice restaurant and great views. Then, weather permitting, the approximately 4 km. walk to Alp Languard has more and varied scenery. The cable car then takes you down to Pontresina. That service is running in the first week of October.
See attached screen grabs.
If you don't want to walk. , the ride up to Muottas Muragl or Corviglia for a view and a meal are both spectacular.