For example, the Gregory Paragon 58 backpack has a volume of 58 liters and is suitable for 4+ night trips if you pack lightweight and for 2-night outings if you typically bring more than the others when you go backpacking
20-30L = day hike 30-50L = 1-3 days 50-80 = 3-5 days So basically the size of the pack equates to how much gear you can carry which equates to how long you can survive in the wilderness
As a serious angler, I have used them all and have developed a good understanding of when and where to use each of them based on personal experience, manufacturer claims, and available research

10.6 grams) optimized long-cast class Target Diving Depth: Consistently hunts and claims the 9.0 to 11.0 feet (2.7m - 3.4m) depth column zone Lip Technology: Specialized Weighted Bill Engineering (Ensures near-instant vertical descent & low-fatigue cranking) Action Footprint: High-frequency, tight and subtle wobbling roll (Entices high-pressure staging fish) Hardware Components: Factory-equipped with two premium ultra-sharp Berkley Fusion19 Treble Hooks Best Application: Ripping over submerged weed edges, offshore gravel humps, secondary points, Bass, and Walleye in Berkley Berkley Dredger 10.5 Crankbait CA$13.99CA$13.99 Select options Quick View Out Of StockThe Berkley Surge Shad 130 Jointed features a two-piece jointed shad profile with a stabilizing FlashDisc and tailored bill for diverse retrievesreel, twitch, or jerk across surface or just below
I suppose somewhere in all those trips I found my love for the mountains