Line bedding is one of those things I've heard of but hardly ever experienced, and that was on the very narrow spools on an old Abu cf. It's never been an issue with backed-up deep spools or shallow ones. I put it down to the excellent line lay and long spools on Shimano's. I'm fussy about filling spools, and I have spools backed to be just right with 100m of 2, 3,4lb or whatever. The backing is wound on under enough pressure to make a firm bed. Some, I've taped over the backing, some not.
I prefer reels to come with a mix of deep and shallow spools. A comparatively high-spec Shimano, a Twinpower xtr 3000 with lots of bearings that I bought at a big discount came with 3 match spools. The reel is heavy and over-powered for 2-3lb lines, but the spools take very little 6 or 8lb line, so I have to match the grey/silver reel with black spools off another model. The deeper spools give me the option.
I prefer reels to come with a mix of deep and shallow spools. A comparatively high-spec Shimano, a Twinpower xtr 3000 with lots of bearings that I bought at a big discount came with 3 match spools. The reel is heavy and over-powered for 2-3lb lines, but the spools take very little 6 or 8lb line, so I have to match the grey/silver reel with black spools off another model. The deeper spools give me the option.