The problem that I have run up against on several occasions is
weight. I could pack more into my checked bag but I am finding that the 50lb weight limit is the problem, not available volume. Here in the GWN, airlines charge as much as $100 for an overweight bag (100Euro for the return flight), limit of one checked bag unless you pay up to $150 for a second bag. I put my riding pants, jacket and boots in a large duffel and then pack underwear, base layers, socks, etc in with it until I hit the weight limit. The rest (including helmet and all electronics) goes into a 50 liter back pack and a messenger bag which I carry on.
On the return trip, if I have bought things, I may leave socks, underwear, etc there to make the weight limit. Cheaper to replace than to pay the "overage" fee.
Because of the weight issue, I sought out the lightest possible duffel bag (yet retaining structural integrity). This is what I found to work the best without spending HUGE money.
https://fortnine.ca/en/ogio-big-mouth-wheeled-bag
It is about 3 lbs lighter than other equivalent bags and that 3lbs is a big deal.
What I really need to do is learn to travel lighter but that is not that easy when you are facing potential temperature/rainfall variability. I am finding merino wool base layers and socks allow multiple day wearing without having to wash them. This cuts down on the amount of those things that I have to take. It is a work in progress.