Hi chesse hole, well i live in Meiringen and work in Interlaken, so i may be able to be of some help. Don't know how old you are, but thought i better warn you, Balmers Herberge is very much known around Interlaken as all the young tourists go there, it's a party place with it's own bar and disco, and it's usually very loud. (one of my mates worked there) There are a lot of great bed and breakfasts in Interlaken, which is cheaper than a hotel and you could come and go as you please.
The 2 Railway stations are Interlaken west and Interlaken Ost. The west is more in the center and has a lot of shops and things, but the ost is where all the connecting Trains go from, i would stay near the west, as it's not a far walk if u need to go to Ost, and there are busses and trains that go quite often.
The train to brienz takes about 20min, to meiringen just over half an hour. It's about 35 km between Interlaken and Meiringen.
The Ballenberg Freilichtmuseum is great, but you need a day there to see everything. You can take the train to brienz or brienzwiler and then a bus can take you directly there. Ask at the railwaystation, then u can get ur trainticket and busticket at the same time.
If you have any more questions let me know. Hope this information helps you