It seems I’ve finally cracked the code, thanks to all your suggestions!
After wandering through mechanical tweaks and firmware adjustments, it turns out that following a BambuStudio software update, my PETG filament profile got a bit scrambled.
I was printing PETG with a fan between 10% and 90% … not ideal! A flow rate of 90% is way too enthusiastic for PETG and likely the reason why my printer started spewing noodles! 
I’ll keep testing and show you a before/after with just a tweak on the fan. The filament’s a different color here, but it doesn’t affect the print quality.
Huge thanks to everyone for your invaluable input. It really warmed my maker heart
