Recommended optics, clothing and equipment, individual species, itineraries, etc.
It really depends on what species you want to see and what you’re up for. Some species (eg: crossbill spp, capercaillie, ptarmigan, dotterel) can require walking to get the best chance of a view. But the length and type of route can sometimes be matched to your ability, whilst still offering the chance for a sighting.
I can offer guiding via the Cairngorm funicular railway, which offers an alternative means of gaining views of ptarmigan and dotterel ( additional charge and conditions apply ).
Binoculars are very useful, 8 x 42 or 7 x 32 being the most popular sizes ( pocket binoculars are often inadequate and the large 10 x can be too heavy ).