How to disable bezels and use scanlines on a per-system basis

[stigzler]

Of course, Retroarch is aces, but the fella who designed the configuration/settings system must have been having a bad year. It's soooo clunky, unreliable and unintuitive via the GUI.

Basically, I'm looking to disable the bezels on all systems and use scanlines on selected systems. I've tried various permutations of:
Settings>Configuration>Save Current Settings (often get Error) / Save New Config (saves as the core name for some reason)
Main>Quick>Overrides>Save Core Overrides
Shaders>Save>Save Core Preset

It's all very shonky. Does anyone have any tips?

[Zing]

@stigzler I think it's easier for you to make a config override file, check this out:

• https://wiki.recalbox.com/en/advanced-usage/configuration-override
• https://wiki.recalbox.com/en/advanced-usage/configuration-override/retroarch-overrides