Using the united.com seatmap from the flight you are selecting will help you figure out which seatguru configuration to look at.

As a basic guide:

EWR/IAD -> HNL appear on united.com as the "767" (this is a 767-400 aircraft) which are equipped with reclining old Continental BusinessFirst seats (aka cradle, aka barcalounger.) These are the standard aircraft for the route. From time to time the route is operated by an aircraft that appears on united.com as the "767-400ER" which will have flat bed new seats.

ORD/DEN -> HNL appear on united.com as either "777-200" or "757-200" and both flights operate with regular domestic first class seats. Compared to other options, from a seat perspective these are the least desirable flights.

IAH -> HNL appears on united.com as "767-400ER" which as you know by now is a flat bed configured aircraft. I do believe this route also has a random pre merger United 3 class 777-200 aircraft on certain days. This particular aircraft has a reclining business class seat that is similar to the business class seat on the "767" designated aircraft and is a cradle or barcalounger type seat.

Side note: If you ever notice a flight operated by a 757-200 and the flight number starts with a "1" it is a flat bed 757-200. Keep in mind, these don't fly the route we are talking about, but just a more you know kind of thing.