Fujifilm have some good lenses to work with on what you wanted to shoot. But do note, the Fuji 50-140 f/2.8 isnt a small lens but you have the alternative to go for the 55-200 f/3.5-4.8 which is compact for hikes.

Fuji system are small and extremely tacky AF for focusing and tracking but at the cost of battery life. Average 400 shots per battery or lesser if you use live view full time. So you will be carrying approx 10 batteries in total. Other than that, its all good.

I shoot with Nikon FF as part time professional and used Fuji but i maintain both system.

My current Fuji setup is XE-2s + 18-55 f/2.8-4, 55-200 f/3.5-4.8. A very simple setup to backup the Nikon giants. I have tried to move to Fuji but I couldn't work without the 600mm lens hence I keep it as a casual backup.

My advice to start on fuji system is get a used body first and get the adaptor to able the use of your canon lenses. Once you have tested your comfort and mirrorless tolerance, slowly migrate to fuji once you see fit.

This way you dont loose much during the transition

Honestly, the X-TRANS sensor is really a magic. It have some of the best high-ISO noise control as it makes the noise grain to looked more film like than the counterparts does by over-processing etc. The image is on-par with the D4 I owned and have better edge on color rendition too. D600 surpass the XE2s but the XT2 will easily surpass most full frame IQ even with just its kit lens 18-55.

So far I am extremely happy with the XE2s I have