Normally yes the switches have to be wired. It is possible to use a wireless switch (with battery) which would have to send a signal either to a smart bulb like a Philips Hue bulb, or to a smart relay/dimmer module which is wired in to the lighting circuit e.g. in the ceiling void. So no it would almost certainly not be a standard momentary switch.
Yes fitting a module like the Fibaro in/near the ceiling rose should mean you do not need a 3-wire link to the light switch - at least for on/off control. Fibaro Dimmer modules are designed to be usable on 2-wire circuits although for also providing dimmer control this might require the module to be in the switch back box. This still saves having to rewire all your lighting circuits.
I personally am planning to get all my light switches re-wired to have 3-way cables as part of a larger project. I am also currently leaning towards using Insteon micro modules rather than Fibaro modules.
Whilst currently Insteon have withdrawn their HomeKit gateway they claim they will be launching a new (better) one at some point, the currently available gateway does not support HomeKit but does support Alexa and Smartthings. Also Insteon unlike Fibaro also make plugin switches and dimmers suitable for desk lamps. As far as I can see you would use the same momentary switches and could even like Fibaro also create a pull-cord momentary switch for bathrooms. However unlike Fibaro there is the possibility of adding HomeKit support.
(Yes Fibaro make a HomeKit compatible relay aka on/off module but no dimmer module and it is HomeKit only and hence not compatible with Alexa or Smartthings as well.)
I would still overall prefer Lutron Caseta but there is no sign of that becoming available for Europe.