Hi Gareth.
The NAP140
does have the same general schematic that applies to the generic NAP250 bridged mode design often seen published on the web. It's the only official NAIM amplifier schematic out there, as far as I know but be aware it didn't fit exactly with any simple amplifier.
In other words, the topology for all NAP models will be correct, but the specifics like resistor values for the LTP and current sources of the various models will most likely be wrong and so is the NAP140 title, when you get down to details. NAP 140 is often recalled as the best sounding of the bunch. I haven't heard them all, but it must be a fine line of difference between some models. I suspect that's the reason Chinese kit sellers named the kits accordingly. Otherwise, I can't think why anyone would make such a blunder.
You might be aware that Avondale Audio's ready-built Naim clone amplifiers were around for some years too, based on the same NAP 250 design but with Les Wolstenhome's own tweaks and variations to the design, which also turned up in his DIY kits, modules, bits and Naim mod. suggestions too. There are some specific parts that even he hasn't changed either - guess why. Some folk also prefer his NCC200 versions to the original Naim products which is reasonable, with hindsight on a design that dates back to the 1970s.
NAP140 supply rails are not 40V (34 actually) and the LTP collector resistors and current source emitter resistors are different to suit the supply voltages of all the NAP series, with some minor omissions such as the RC filters in the driver bases of the NAP90/early Nait series.
In the big NAP140 Ebay kit thread, the subject of sound quality turns up a lot because that's what most builders are hoping to find or at least get a taste to say yup, I know all about Naim sound and it's crap/amazing/so-so etc. - my DIY build proves it.....

My own experience is not huge but I've built several stereo NAP kits over several years and listened for many, many hours, comparing them with mods, as original and around 15 more different clone kits built by friends. I even own an original NAP140 myself (when its not on loan
😉)
As far as defining sound quality goes, Naim still adhere to a few specific component types for reasons that become clear when you build a clone with whatever cheap parts or even modern, high Ft parts that ordinarily, would best suit the applications. The biggest mistake is to fit the D667/B647 VAS transistors now supplied or other low Cob transistors too - there goes that essential Naim sound you find with ZTX653/753. Why? Look at Cob -30pF! look at Cdom- only 39pF. Compensate by adding capacitance as you will but the added distortion of high Cob transistors is actually desirable and necessary for Naim sound but not easy to replicate any other way, if at all.
I think the secret sauce is not so much in some special design technique, but an adherence to what we'd now call errors in part selections in the early days of Naim and perhaps with the first series NAP200. Smart as he was, Vereker was not an engineer and did things his way, putting his spin on the pleasing and surprisingly successful results. Even today, professionals still pooh-pooh the general design despite its phenomenal success and survival over decades.
The clone kits though, will be disappointing as they come, even the more expensive kits and built modules with quality components, if you are familiar with the Naim sound quality you seek or perhaps you're a casual audiophile looking for something interesting in retro audio. You're going to need an original model or very close, to be confident that subjectively, you do have what you were you're aiming at - not an easy ask at all.
for reference, the NAP250 and generic NAP schematic: