Can we use "Eurail Global Pass" with "GOLDEN PASS TRAIN" in Switzerland ?

There is no need to make reservations unless you are travelling during the high season in the summer and you want to be absolutely sure to get a seat. My daughter and I travelled the route from Spiez to Montreux in the beginning of August this year and then there were few travellers. 

A tip is to make a stop in Gstaad or any other village that the train passes.

It should be included, maybe a reservation needed. 

For your information, from timetable change 11 DEC 2022 the Golden Pass Express will run on all the train line, without changing train set due to new gauge changeable train sets from Interlaken to Montreux. Maybe due to this, the reservation policy for this train may change. I would ask directly the train company that runs this train: MOB and BLS. https://www.gpx.swiss/en/ 

Can we use "Eurail Global Pass (for non European citizens) "GOLDEN PASS TRAIN" in Switzerland ?

Yes. There is no difference in the validity of the Eurail pass and the Interrail pass.