I've got real world experience with just this dilemma....Was in Scotland (TREKKING in the Orkney Islands) last year. I too have a 5Div and an RP (wound up selling all of my M stuff and got the RP with the RF 24-105). After lots of consternation, went on that trip with the RP, 4 batteries, the RF 24-105, my EF 100-400MKii, and EF 16-35. I have the control wheel EF-RF adapter. All fit into my backpack but I also brought a lightweight non-camera messenger bag for times I would be walking around towns.
My bottom line: The EF lenses were a bit heavy but the size and weight savings for the camera was welcome. Except for things like "bird-in-flight" photos, I never missed using the 5Div. The in-viewfinder histogram was very helpful. The RP focus was dead on. Any issues with sharpness were my fault, not the camera. The high-iso shots are quite reasonable, and in my experience, I feel like I am able to raise the shadows in post with better outcomes than when I use the 5Div. The RP never used more than 2 batteries on any given day (but the battery life is certainly not as good as with the DSLR. We had a bit of "weather" because this is, after all, Scotland. I kept the camera in a Lenscoat Raincoat and, if the weather was truly awful, carried an umbrella. Maybe I was lucky, but never worried about the lack of weatherproofing in the RP.
Did about 1200 shots with the RF 24-105, 200 shots with the adapted 100-400, and 14 shots with the WA, but that will vary with you interests and styles. My point is, based on my experience, the RP makes a very reasonable travel option.
For me, I will someday give up the DSLR and go totally mirrorless. Just not "there" yet. Do enjoy the trip.