>> What is the easiest way to see which are the "fast" or direct trains...on the webiste or map of the SBB?
The fastest routes for getting around in Switzerland (generally speaking) are fast because they go through the flatter parts of the country and/or take valley and tunnel routes, which is great for commuters.
However, if you are a tourist, you miss out on so much by choosing the fast routes over longer, more scenic ones. Scenic routes tackle the mountains and transport you through stunning scenery instead of zooming underneath it in a tunnel or detouring through the flatter parts of the country to avoid the mountains.
>> when looking for B&B's, accommodations, etc., are there taxis to get you to them if they are not by the train stations?
It is generally quite easy to get accommodation within easy walking distance of a station, so for convenience and best use of time and money, I would recommend you stay near a station, or at least near a bus stop (but note my comments about bus services below).
When considering which accommodation to choose, look up the address in Google Maps, then zoom in to find nearby railway stations and bus stops. If you hover the mouse over the bus stop or railway station logo (or tap it on a hand-held device), it will give you details about the official name of the stop, and for buses, the number/s of the bus routes that stop there. You can then use that information in the official Swiss Timetable to find out how to get there. Lucas has already given you the link to that.
If a bus would be necessary to get to your accommodation, make sure to inform yourself before booking about frequency of service and the time of the first and last bus service of the day, including weekend services.
>> As we are in this Interlaken Region at this point what would you recommend
Interlaken itself has the least to offer of any town in the Jungfrau Region in my opinion. It's a good transport hub and has a lot of shops, restaurants and hotels, but has little charm. Personally, I would give it a miss.
The charming traditional chalet-style villages of Lauterbrunnen, Wengen, Grindelwald and Mürren all have wonderful scenery, so I would recommend staying in one of those villages.
- Lauterbrunnen is on the valley floor, so views are up to the cliffs on each side of the valley, and to the mountains at the valley end. The Staubbach Falls are also a prominent feature in the village.
- Wengen is on a terrace above the Lauterbrunnen Valley, and has views down to the floor of the valley, across to the cliffs and mountains on the other side, including the Staubbach Falls, as well as over to the Jungfrau Massif. Behind Wengen, the Männlichen massif looms over the village.
- Mürren is on the top of the cliffs on the opposite side of the Lauterbrunnen Valley from Wengen, and has remarkable close-up mountain rockface views.
- Grindelwald is also surrounded by stunning mountains. It has more shops, hotels, restaurants etc than the other villages, and a busier, more commercial feel. It also has traffic.
Wengen and Mürren are car-free, which makes them extra special in my opinion. Hotels usually have small electric vehicles, which they use to pick up guests and their luggage from the station on the day of arrival, and to drop them off on the day of departure - but check before booking.
Here are some links to information on this website which will assist you in planning how to spend your time in this beautiful area, and for finding accommodation: