Hi Pringles
I’m not too clued up on Devol but just skimming their site it seems they use tulipwood/poplar for their frames, doors etc. My understanding is that Smallbones etc use this too ... it’s pretty standard amongst the “top” brands, independent cabinet makers, etc. Although I suspect the top end will offer different timbers (at a cost no doubt).
Maple (specifically hard American maple) is an awesome choice for an in-frame/inset “ style painted kitchen when you don’t want to see visible grain. It takes paint really well, the grain is easily filled to give a beautifully smooth finish which doesn’t show through and it is exceptionally “hard”-wearing. 
TBH I don’t know of any mainstream manufacturer that offers a standard range with hard maple frames and door rails and stiles. In my experience it’s more the domain of a truly custom/commissioned kitchen. Often only the frames are made of maple to reign in the cost as the price difference between US maple vs poplar (the usual choice in this instance) is huge.
So, in a world with limitless budget a timber like hard maple for this style of kitchen is the ideal. Another similar quality wood which paints well and is hardwearing is beech (also not cheap to have the lot made in beech).
Next comes poplar/tulipwood etc. Whilst much less hardwearing than maple or beech it takes paint really well, is in abundant supply, is as stable as a timber can be in a kitchen environment and it doesn’t show grain. Alder, used by PWS on their 1909 range, is a marginally harder timber than tulipwood but only negligibly so and shares all the other characteristics re finish etc making it an equally suitable choice.
So at this level there is very little difference (if any) between the quality of a tulipwood/alder frame and 5 piece door made by smallbone, devol, new English, handmade kitchens or even 1909. The big differences, certainly to cost, come with brand status, service (to an extent) and other elements regarding the kitchen as a whole (eg ability to customise, use exotic timbers or veneers, expensive accessories etc etc).
Choice of cabinet material to determine quality of the overall kitchen is something that I’m less convinced by. Many makers will say that birch plywood is the best choice. It is certainly at the top end of choices but it’s often sited as the reason why “cheaper” kitchens use MFC or MF MDF or veneered MDF. While birch ply costs a little more than quality MFC boards or MDF veneered or MF boards (note that these boards are not all made the same and cheaper kitchens will use poorer quality chilpboard cores AND melamines) the cost across an average kitchen is relatively negligible when compared to the total cost of the kitchen including doors, labour in making and finishing, cost of hardware etc.
For all the arguments that plywood swells less when submerged, it still swells enough to warrant a new unit, panel etc. when there has been a significant enough leak to seriously compromise the integrity of any of the boards. Furthermore, it’s composition closer resembles solid timber than mdf and mfc which means that it behaves more like timber than the other manufactured boards hence it will move more than they do. MDF gets a bad name but takes paint beautifully. However, chipboard and plywood are quite a bit lighter than MDF which can be an advantage (they certainly sag a lot less under their own weight making them a better choice for shelves especially in wide units). MDF and chipboard both take glues for melamine and veneers very well and won’t show any grain (they don’t have any). Plywood needs finishing and some feel that a top quality melamine is actually a tougher material than any lacquer or oil that one would apply to a plywood carcass and will therefore perform better for longer with bowls, plates etc being moved in and out of units. The arguments for and against each board go on and on. Many are firmly in the ply camp...I’m on the fence as I think they all have their merits. Importantly if it’s birch or poplar ply (or a quality oak veneered ply), quality MR, deep route, etc type MDF or a reputable chipboard (eg Egger, Krono) i don’t think any are a bad choice. Much more important is board thickness (including back panels) and manner of construction.
What I will say is that in my opinion Innova are not the best quality kitchen component manufacturer. Personally I think Burbidge and PWS make better quality (and pricier) products (possibly Multiwood too but it’s been a while that I’ve seen their stuff). In fact I’m sure that DIY used to use pretty much Burbidge and PWS exclusively (I’m going back a few years) but it seems they no longer do.
Lastly I wouldn’t compare the Helmsley with Devol tbh. Nor would I put it next to 1909 either. 1909 is a form of production run Devol, New English,etc style kitchen which should make it cheaper but still sort of puts you in that “category” of kitchen (it’s certainly not a “cheap” kitchen). However, with any component supplier the overall quality of your kitchen is also massively dependant on who manufactures the units and fits the frames and doors.
I would compare Helmsley to PWS Milton In Frame and all those similar offerings from other manufacturers.
Lastly, to end what I’m sure is now a boring rant to all who have read this far, I would advise against Blum style (ie concealed) hinges with in-frame kitchens such as these. These hinges are great because of their ability to adjust how the door hangs after it’s fitted (and soft close). However, inherent in their ability to be adjusted is the fact that they need adjustment over time. With overlay doors this is less of a concern as there isn’t a frame 1 or 2mm around every edge of the door. When the doors inevitably drops, it will likely bind on the frame, thereby rub paint, etc. Note this isn’t the hardware failing it’s just its nature given it’s function. Yes it can be readjusted but eventually it reaches its limits in this regard. Obviously it can be replaced and you start again but how many do this? Now, keep in mind that with 22-24mm hardwood doors from 1909 right up to the elite there is a lot of weight on the hinges and this will only make it worse/happen more frequently. So, even when the 1909 website showcases the product with these hinges be advised of the above.
It’s no coincidence then that the big, quality brands use traditional butt hinges. This requires much more precise cabinet work by the maker and therefore increases overall product cost. Here there is no adjustability, either the cabinet maker hangs the door well and it functions and looks well hung or, well, it doesn’t...
I hope that helps. I’m sorry it’s long...I kinda got carried away there.