Does the heated surface warm the water or just the tub?

It warms the back and neck contact area of the tub itself, not the bathwater. You set the temperature, and the surface stays warm while you soak.

Does it need a dedicated electrical circuit?

Yes. The heater needs a power connection, so plan an outlet near the tub and check local code for GFCI protection before installation.

How does it compare with a whirlpool tub?

It gives quiet warmth and a long soak instead of water jets. If you want massage action, a whirlpool or air bath is the better fit; if you want a warm, still soak, this is simpler and has no pump to maintain.

What size surround does a 72-inch drop-in need?

The tub drops into a deck cut to its rim, so the surround must be built to the tub's exact rim dimensions and support its weight. Have the tub on hand before framing the deck.

Can it be used with a shower?

It is a bathtub, not a tub-shower combination. A shower would need its own enclosure and waterproofing above the tub.

Does it match other Memoirs fixtures?

Yes. The rim detailing is designed to pair with the rest of the Kohler Memoirs collection, such as its toilets and sinks, for a consistent traditional look.