The gallery style is just a general label, the actual plugin styles are inside the sidebar menu: If you had CSS added it would be what you added in the box under Settings/View (see screenshot for what I am referring to for instance I had selected left for green in this screenshot)
I.E these are styles that are included and each one has a description of what they effect:
Under Settings/View under Gallery
On the inside slide bar under view there are names for the various styles, i.e.
AI Swarm full
default ((The default Store Locator Plus layout and CSS shipped with the latest release. This is the basic layout for the locator. It allows default browser and website themes to dictate the element styling.
Supports Premier Search Form Styling options, Experience placeholders without labels.
Resets the following settings to the initial Store Locator Plus defaults:
Locator Layout , Search Layout, Results Layout, Map Layout, Bubble Layout, Google Map Style.
Last Updated: Feb 21 2018))
If you are changing the results layout in the results layout itself it may be overridden the next time. You should save any CSS under the Settings/CSS and use a plugin style that allows for CSS such as Metropolis
when you view the various styles (from the inside slide bar) there will be a description that explains the layout results you can expect to see. (themes can override them as well)
Example” Metropolis styling attempts to overcome the vast differences in class. Takes over more of the CSS styling than usual.
This style is updated with additional rules on a regular basis whenever someone reports a misbehaving layout. Select another style, then re-select this style to reload the latest rules.
Style Guide: right pad 2em, vertical margin 1em, result line height: 1.5em
2017-Nov-23 : right pad on span.slp_result_email/fax/phone/website, single line on span.slp_result_street/street2/citystatezip/country/hours, vertical margin below country and above hours, drops Foundation float:right on div[class*=”column”]