I also had the extruder drive slipping backwards (clicking sound) as well and narrowed it down to a Cura update that had changed my Ender 3 machine settings from Marlin to Marlin (volume metric).
Once changed back to Marlin, all is well now. No over extruding. Before reversing the change, I had to reduce the flow rate to 53 %. Now, I’m back to 100 % and ...
I wouldn't worry about that overhang. It should settle in a few layers. Just make sure you have a decent cooling fan on it.
Given the fact that you are making a helmet, I assume you are going to sand and apply putty to the whole thing at least 2 times and then sand in increasing grit. A little filing on that overhang will be an easy task.
If your printer has only one extruder, leave the Extruder G-Code empty. This setting is useful for multi-extruder printing (e.g. multicolor). The extruder G-Code runs each time you switch to and away from that extruder, and can be used for stuff such as retracting a filament when switching.
It is a little annoying, what Cura is doing for me is forcing to wait. On start G-code I have:
; Ender 3 Custom Start G-code
G92 E0 ; Reset Extruder
;*** Start Dual Nozzle/Bed Preheating ***
M140 S60 ; start preheating the bed
M104 S200 T0 ; start preheating hotend
G28 ; home
M190 S60 ; heat to Cura Bed setting
;*** End Preheating ***M420 S1; Load ...
Likely underextrusion. The Ender 3's extruder is particularly bad at PETG and slips a lot unless you go really slow, like 3 mm³/s (about 40 mm/s at 0.2 mm layers and 0.4 mm line width) or lower.
For a long time I thought this was a limitation of the material, at least without a really powerful hotend, and wondered why anyone liked it. But after replacing the ...
The density of the filament can be specified in the material model of the filament in Cura (Preferences -> Configure Cura... -> Materials and click on the material/filament you are using to slice your model for PETG), look at the value behind Density, the PETG filament I use is using 1.28 g/cm³ (PETG Economy Black -> Specification >).
This field ...
Z offset in Cura
Z offset in Cura is nothing more than an additional increase/decrease in height calculated throughout the whole file. This does require the installment of a plugin from the Ultimaker Cura "Marketplace" called "Z Offset Setting" by developer "fieldOfView". This should work (if not, this implies the plugin is ...