Ariston is marginally smaller but no where near as good as Miele both in performance and service. You loose quite a bit of capacity.

Asko gets higher temps for whites and to disinfect but not as good in terms of service or reliability. It is a bit shorter but deeper.

It seems your perfect washer would be V-Zug but unfortunately they don't sell them in North America.

Bosch also makes compact washers and driers. These look like the models they sell in Europe. The European models are considered good (we had one for years; it was excellent). ~24" is the standard size in Europe.

Here is a link that might be useful: Boch compact washers and dryers

For your application Miele or Asko are the only good bets.

The Bosch has quality issues especially long term, I've had two pair over the years and all have needed service and parts, and one pair was scrapped entirely. My miele is still going strong.

There are a whole bunch of tiny Asian top-load washers sold by the likes of Haier and Avanti that have a 16" to 21" square footprint, along with (usually 120 volt, ventless) dryers that are only about 15" deep. The latter are not condensation dryers, rather they just run their exhaust through a filter and into your room, which tends to get warm, damp, and dusty.

a top loader doesn't make much sense in kitchen cabinets , underneath a countertop.