I checked the time table that Lucas linked to. I searched Paris to Wengen, with "Basel" in the via box.
It looks like you could take the 0723 TGV Gare de Lyon. You'd get to Interlaken Ost at 1228, after change of trains at Basel and Spiez. You'll get to Wengen at 1319. The trains from IO into the valley and up on the mountains are slow; some are cograil sections.
Presumably, you will not have a whole lot of luggage. Be glad that you don't have to transfer at Bern. Not difficult, but a very busy station.
The connection at Basel SBB is only 5 minutes, but you come in on Platform 9 and depart on Platform 10.
The station map shows that those tracks are on the two sides of one platform.
At Spiez, the connection is only 3 minutes.
That is certainly from one side of the platform (track 3) to the other (Track 2). It is a small station.
At Interlaken Ost, you have 7 minutes. You will go from Platform 2 ( the main line track) to Platform 8 ( the narrow gauge line into the valley. The station has some narrow stairs, but you will be going with the flow and that will be enough. The trains into the valley may have two sections...they separate at Zweilütschinen, and one goes to Lauterbrunnen, the other to Grindelwald. Take care to get the right section. You'll have lots of guidance.
A 12 minute connection at Lauterbrunnen is generous.
As for rail passes, I see that Lucas did not answer that question. I'd ask again. That is a subject on which I am not an expert, and there is a regional pass to consider, as well as the ones that you mentioned.
Normally, I'd guess that the half-fare card is the wrong choice for such a short stay, but it gives a bigger discount for the Jungfraujoch.....which is an expensive trip.
Once you are in the valley, it does take a while to get back out to Interlaken. However, from Interlaken to Bern is a short trip, with frequent trains, if the weather is too cloudy to enjoy the mountains. 52 to 56 minutes. The ones on the hour have no change of trains.
The hike that Lucas mentioned is super. RThe trail may be snow covered. If so, make sure that you have sturdy hiking shoes or boots, and a hiking staff. You can also walk on the valley floor ( Lauterbrunnen to Stechelberg), and from Grütschalp to Mürren:
www.myswissalps.com/ju ngfrauregion/activitie s
Scroll down for hikes.