Which is better for a couple?

The Queen. A Twin is too narrow for two adults to sleep on comfortably. The Queen gives each sleeper enough room to turn over.

Is the Twin the same mattress as the Queen, just smaller?

Yes. Both are 14-inch hybrids with gel memory foam and pocket coils. The only real difference is the bed size and how much space it takes up.

Expect similar lifespan from both since the materials match. A Queen shared by two people may soften faster in the middle than a Twin used by one sleeper.

Is the Queen worth stepping up to over the Twin?

If two people sleep in the bed, yes. For one sleeper or a child, the Twin covers the same comfort without taking up extra floor space.

Does either work on an adjustable base or a sofa bed?

The Queen listing mentions a sofa bed style, but check the base requirements before buying. Pocket-coil hybrids generally need a solid or slatted foundation.

The Eurotop and foam layer give it a medium feel with a plush top. Owners who want a very firm bed often find it too soft.

Tryagat 14" Queen Hybrid Mattress vs Tryagat 14" Twin Hybrid Mattress

These are the same Tryagat 14-inch hybrid build in two sizes, so the choice comes down to the bed, not the mattress. The Queen fits two adults and is the better pick for a primary bedroom; the Twin is for one sleeper, a kid's room or a guest nook. Owners rate both 4.4 out of 5, with the usual hybrid mix of praise for back support and complaints about edge softness and a short break-in period.

Choose the Tryagat Queen if two people share the bed or you want room to stretch out.
Choose the Tryagat Twin if the bed is for one sleeper, a child or a small guest room.

Prices

Tryagat 14" Queen Hybrid Mattress: $189.99 at Walmart (checked today)
Tryagat 14" Twin Hybrid Mattress: $126.99 at Walmart (checked today)
Difference: the Tryagat 14" Twin Hybrid Mattress is $63.00 cheaper than the Tryagat 14" Queen Hybrid Mattress today