"Do most find that subwoofer settings are not perfect for every song you play ??"
Yes it will always be recording dependent. Nothing is mixed the same. If you have a high enough resolving system you will even find this from track to track on the same album. It's frustrating.
The boom coms from over pressurizing the room with bass when it gets trapped and has nowhere to go. Most people will say, and I agree, that two subs are much better than one because it will lessen room node/modes.
There will be many people typing that you need a dozen subs, you need room correction, you need to replace all your lamp shades with ones made from Panda etc. Your best bet is to employ two subs and get them away from the corners so they don't couple up. Good luck!