I haven't looked at a muffler, but it's a good idea.
Regarding chamber heat, I still haven't quite dialed in my PLA settings. On really big prints, like a router template, I get some peeling in the corners (exacerbated by the chamber fan). Adjusted the settings to run at different temps, fan settings, dried the filament, all of which improved the results, but didn't eliminate the issue. Gonna try a smooth finish plate instead of the textured one that came with it.
I had similar issues with my Prusa Mk3 when I first started using it, but it was easier to tune out.