Dealing with bass/sub bass is not easy. It's not just a matter of trapping a little bass, it's what frequency are you trapping. It's relatively easy to manage reflections down to 200 hz. But lower than that needs volume. A foot of fluffy, can get lower... 160, 2ft, 3ft, 4ft...100, 80, 60. So sub bass, with such long frequencies, takes thicker traps... Or you go to resonance type traps like hemholtz tuned for what you are trying to fix. "IF" you wanted to get low... It becomes natural in a long room to do an end... 4ft of fluffy, on front or back wall as an example. That is not that crazy. I know you want windows on front wall, don't know if door is on back... But even if you can do rear wall... You will trap bass that hits it down to 40 at least. But even with that, you still have way more surface area of side walls, ceiling and floor all reflecting omni directional, long wave bass. I'm just trying to show that doing that, or both sides down room in ceiling corner is just not that much compared to the rest of the room... All of it reflects.
So then that sounds crazy, and more than you want to do, so what does that leave... Well you deal with reflections down to 200hz. That's easy. Treat first Reflection points with good absorbers... Like 4" rock wool. Use diffusers where you please... And you are still left with bass problems. That just means you have room modes, standing waves, and nulls and peaks. As long as your listening position is not in a peak or null, then there really is not a huge problem. That is all a matter of distances of speakers and listening position in relation to boundaries and reflections. But again, find the right positioning and LP in neutral position... The room mode 4ft away doesn't matter much. I don't treat my room for it to sound good everywhere, I only care about LP. Home theaters care about everywhere more... You need good bass trapping... Or you go with multiple subs that can change and counter those peaks and nulls. While many believe in dual subs, I tried in my room with measurements and could not find an ideal solution for my weird room. The juice wasn't worth the squeeze for "ME".
So it's not really about too much bass trapping taking up too much of the room. You can only do so much, and it's super difficult to eliminate all bass problems everywhere in the room. Treat what you can, and deal with rest with positioning and measurements. Near field helps by getting speakers further from walls which delays reflections. Being closer to speakers requires less volume which lessens reflected energy. Just another strategy to remove more room from the equation. It's a matter of personal preference of how much room you want to remove, but SBIR and bass peaks and nulls are measureable and repeatable. That's not subjective.
With all that said... Back to your first question... It's not a that you can't make listening on long wall work. You can. It's just that everything has consequences... Both long or short walls. With everything we know about speakers in rooms, long wall causes more problems than they fix. It depends on a lot of factors if it's "better". If it is your only option, it becomes "best". But being on narrow axis, you really need to treat front and rear wall more which means you squeeze in more. Less distance to fix reflections.