Are these two dwarf hamsters living together as a pair or separately? If as a pair then you want at least two wheels. I also think an open wheel is better for a pair so they can both hop in and out easily while it’s spinning. An 8 or 9 inch wheel is fine for dwarf hamsters. The standard used to be the 6.5” silent spinner but it’s not the same since a manufacturing change and many people have found them too stiff to spin properly.
The 20cm wood trixie wheel is a silent wheel. You could get two of those or one of those and a larger wheel with a deep running track that’s easier for them to run in together. The wood trixie wheel really needs painting on the inside with plastikote though so it’s wipe clean (including painting the cork running surface).
Assuming they are living as a pair, the set up needs to be carefully done to avoid them falling out and fighting. So no levels or shelves (they get territorial and one can claim the level leading to fights). Any tubes or tunnels need to be large enough they both fit in easily (eg Pringles tubes) so one can’t block the entrance. You need at least two of everything - wheels, houses, water bottles and food bowls (or no food bowls and scatter feed). Houses need at least two entrances - multiple entrances are good. So one can get out if the other guards the door.
With all this you have a good chance of keeping them together. It is very common for them to start fighting though so the slightest sign of that (or bullying or dominance) then separate them - so you need a specific are cage or bin just in case. In which case you’d need two wheels anyway.
So I’d get the silent 20cm trixie wheel as one wheel - and a Syrian sized deeper second wheel so they can run easily together. Maybe the larger 28cm trixie wheel as that is quite a bit deeper. Or the one Ria linked. I actually got the 9” Rodipet wood wheel for our dwarf Robo which doesn’t have a lip. Also silent and height adjustable. But they are expensive. That would also need plastikoting.
Houses are easily made out of tissue boxes or shoe boxes with holes cut in. Best if they are open underneath and sat on the substrate so they can tunnel in and out as well.
https://www.rodipet.co.uk/exercise-w...ise-wheel.html
Whichever two wheels you get I’d suggest getting a 6.5” flying saucer as well if you have the space in the cage - they do well with 3 wheels and options.
They may sleep in the same house or run in the same wheel together but they always need an alternative option so they can do things separately if they need to at times.