We are nailing down details on upcoming master bath remodel. I'm stuck on tub fillers and hoped for some advice.

We will have a very big Sanijet 680 tub which has an operating fill of about 90ish gallons (125 max). We have a lot of water pressure and I'd like to find a filler with a high GPM.

The tub will be undermounted in an oval deck w/ tile surround, to look freestanding. The deck will probably be too narrow and close to tub edge to accommodate a deck-mounted filler. I was planning to use a freestanding filler, but stumbled on the Geberit Cascading Tub Filler. It is rated at 18 GPM.I really like the simplicity.

Does anyone have any real-world experience with this filler? I know little about the mechanics of plumbing. Could it be used with a diverter/handshower?

A hand-shower in the tub is as important to me as high GPM.

The fixtures in the rest of the bathroom are Hansgrohe Stark.

I'll also ask in a another post, but can anyone recommend any high GPM Freestanding fillers?

Thanks!