Well, there’s only one Atrax robustus, but many mouse spiders and trapdoor spiders. There’s some really strange looking trapdoor spiders. Also, mouse spiders can refer to spiders that are in the genus Scotophaeus. It depends on the species and genus whether they are very different looking or not.
If you're still curious, funnelwebs have more forward pointing fangs and are completely jet black most of the time with a very glossy carapace. The legs are often very pointed and their spinnerets are visible when the spider is viewed from directly above.
Trapdoors have absolutely tiny spinnerets and usually have feet that look less pointed and shorter legs. Many of them also have hairy legs, and the majority of Australian species that share the same territory as funnelwebs have striking metallic sheens on the carapace which is covered in alot of flattened hairs. However it starts getting tricky to differentiate when you look at something like Aname Imanica compared to a random funnelweb species.
Honestly, mouse spiders look so different from pretty much any creature on the planet that your better off asking about the few similarities between the 3. A huge, misshapen head with the front sharply raised upwards from the back. They have a weird trapezoid shaped abdomen and huge, bulbous fangs that work more like pliers than daggers, facing into each other rather than running parallel. They are very stout and chubby with almost disproportionately short hairy legs making them disadvantageously clumsy outside the burrow. Overall uniform black colourarion across all species except for the males of M.Occatoria and M.Bradleyi.
That's all I got