How to change existing DTH for different UI? (“Open/close” to “On/off,” etc)

I’m working on cobbling together a “Power Outage Monitor” using an Aeotec Gen 7 Contact Switch.
Basically I’m using the dry contact capabilities, along with a 5v relay, 5v-3.3v power converter and a diode along with a 5v wall wart power supply to do the mechanical bits…

Basically, the 5-3.3 powers the Aeotec (because in dry contact mode it eats batteries), and if the wall power goes away, the relay drops and the Aeotec keeps sending status via Z wave connections. Cool. That all works…

Now I’d like to have a Device in ST that looks more like an outlet than a contact, reflects power status (ON/OFF vs OPEN/CLOSED) and maybe some slight different messaging and UX. I think I need to copy the Aeotec provided handler, tweak some things and good to go?
Change the icons
Change the status types
Change the default outputs a bit
Maybe create a custom ST App, but i could make do with existing “Notify Me When” SmartApp

Looking for insights. I can code a little powershell, but stumbling thru Groovy and the IDE.

Where do I find all the icons available, etc.

Anyone already taken this on?
Any insights as to modding the Aeotec DH?

Are you talking about the new app? You can’t have custom layouts. You need to find a template (vid) that supports the features you need and work backwards from there.