From my testing it sounds better without the cover, of course if I use the boot I will put the cover on.
There are quite few options for you, if I were in your shoes I would take a trip down south to Five Star Car Stereo at FL. Check their Youtube channel, one of the most professional shops...
Taycan 4S Subwoofer Upgrade (Bose from Factory)
I decided that the bass provided by the Bose system wasn't sufficient. I contacted a local shop and booked an appointment for mid-September. On the morning of the appointment, the shop informed me that they didn't have the components I requested...