Brienz: small town, nice for a stroll by the lake, but not a place to stay in my opinion
Interlaken: here you have the LHW member Victoria-Jungfrau Grand Hotel & Spa - it could prove a good home base to discover the area - bigger town than Grindelwald or Lauterbrunnen - Interlaken is not the cute alpine town you might expect, though, it's not that nice in my opinion (of course it's all relative) - the surrounding lakes Brienzersee, Thunersee are quite nice and have some impressive waterfalls and caves to discover (e.g. St. Beatus).
Grindelwald: I would add the Bergwelt Grindelwald to the already mentioned Boutique Hotel Glacier. And I concur that both are nice but not top-tier like the other hotels mentioned. I also saw the Aspen alpin lifestyle hotel Grindelwald on the map - but have not yet visited it myself.
While you are there you should at least do: Jungfrau Joch by cog railway (expensive but an experience that is worth it at least once) and go to the beautiful Lauterbrunnen valley.
All that said: as others mentioned, the car-free Zermatt or Saas Fee are the more romantic and "alpine" options
Hotel recommendations:
Saas-Fee: the Capra
Zermatt: the Cervo or Chalet Hotel Schönegg
Honorable mention: Not to forget that Lucerne now has a Mandarin Oriental by the lake, quite nice.
Shameless plug: if you're still looking for someone to give you Virtuoso perks at the Chedi and the others, send me a pm
