Like Tonygoy I too found my way to Olympus replacing Canon specifically because of the size for travelling with guests - also so as not to usurp them with their gear and big plus it all fits in as carry on luggage. Olympus OMD Em5 ii with a scattering of lenses
But I got to Olympus from a Panasonic GF1 which I brought specifically for Kilimanjaro together with the 14mm f 2.5 pancake (equivalent 28mm) 20mm f 1.7 Pancake (equivalent 40mm) and the collapsable Olympus 9-18mm zoom lens.
For me I wanted Publish grade optics and that setup certainly lived up to it.
Unfortunately Panasonic lost the direction after the GF1 with the GF range the GM5 is an attractive option too.
9 years later and Ive converted to Olympus love its 40-150 f2.8 Pro lens with 1.4 extender (equivalent 80-300) and that 75-300 zoom (equivalent 150-600). Their 45mm f1.8 (equivalent 90) is also a show stealing lens.
Samyang make a ridiculously small 7.5mm f3.5 manual focus fisheye lens (equivalent 15mm)
The 300mm f4 (equivalent 600) is on my list when I go to the OMD em1 mkiii
For ultralight weight Im using a Canon SX740 camera with 2 batteries - this lasts me a 6 day hike its 24-960mm lens is really useful. 4k is great and Image Stabilisation is actually useful.
The Panasonic FX80 is another good option that has a really useful 20mm wide angle and 1200mm long lens is actually very attractive for its larger size
But if I had no budget then the Sony RX100vii would be my mountain camera of choice. with its 24-200mm f2.8 - f4.5 lens and 1 inch 20MP sensor coupled to a magnificent autofocus system its worth its price (to some people). Most importantly its 4k video accepts a mic input.
One last thing the Canon and Olympus integrate really well with your mobile phone to control it via wifi and download images to share via WhatsApp quickly.
Ooohhh one last last thing - Olympus Live view (the multiple exposure stacking star trail mode) is the absolute bomb - not seen this integrated in a camera as well as Olympus.