If the timing is right and the cows are still up there, I highly recommend visiting Männlichen. In my experience, the cows are often right near the gondola station, you enter into their field and often have to walk right past them to reach the restaurant. These cows are particularly accustomed to people, making it easy to photograph them up close. However, when hiking in less touristy areas, it’s always wise to keep a respectful distance from the cows.
According to the SBB, the journey to the top of Männlichen takes about three hours one way, so it’s unlikely you’ll have time to visit more than one location. Also, be aware that you may need to take a replacement bus bypassing the damaged area in Brienz—this isn’t a big issue, but it’s something to keep in mind.
If your priority is seeing the cows rather than the Bernese Oberland, you can find a list of cow parades here. Simply narrow down your dates and location, and use the map to see which events are near you:
https://www.myswitzerland.com/en-ch/experiences/events/events-search/?rubrik=alpinefestivals
Wassen, in the canton of Luzern, will have one on Sept. 14th
https://www.luzern.com/de/event/alpabzug-wassen