I think Symbols be what you're looking for: https://sketchapp.com/docs/symbols/
Turning something into a symbol allows you to use it in multiple places and then edit it from your "Symbols" Page to update it everywhere.
First, I would say that a prototype is an impermanent thing that you make to answer a question like "do people know to click on this button when it is in the left corner." So the design you use should be to solve that question. Your developer probably won't care about the layout of your prototype as you will usually need to update your designs based on the feedback of the prototype. I design for the device I will be using for the testing. No need to overcomplicate the designs by making them scale to different sizes.
But if you are building mocks and a design system to give to the developer then you should sit down with them and any other key stakeholders and discuss what you are building first. Are you going to build for Android and iOS, or just iOS? Then determine what os you will support and what phones. iOS is great for backwards compatibility so I would design for the smallest phone possible at the beginning. Make sure all of your content can fit in the least amount of screen size. For iOS, this is 320dp. That means in sketch create artboards that are 320 pixels wide. Do not make artboards at native screen resolutions. Its way simpler to design at 1pt = 1 pixel and then export everything bigger later. When you start to build out the components of a view, a header for example, think about how the elements of that component relate to each other and how their position would change if the screen got wider. Don't worry about taller since everything is usually in a scroll view. Decide whether things should be absolutely positions to corners, or move based on percentages, or scale as the component scales to fill the view.
Here is a link to how sketch allows you to build a constraint based layout:
When you open up Mirror on your device the option to connect to the device will be prompted in the upper right corner of the window, such as Library or Plugin updates.
I recently released a series called The Sketch Course
https://www.youtube.com/playlist?list=PLLnpHn493BHHUaj6JcNbGC9_7dM8Utf9W
Other than that, I'd recommend the official docs if you are looking to read.
I've become a fan of Sketch. They just updated their file format to be completely open JSON, so others can easily understand and manipulate it. I've used Photoshop and Illustrator for a while, but Sketch is much more suited to UI design because of some of its toolset.
What layers are you referring to? Is this about the Sketch Mirror companion app, or something else?
Forgive me if I misunderstood, but this subreddit is for the macOS vector/UI Design tool Sketch
Yes, artboards and symbols are actually pretty much the same thing in Sketch, except for the special symbol functionality.
Artboards are used to represent a page or screen of your project. They act as a container for these screen elements (text, shapes, symbols, etc). They are also used in sketch for prototyping, and will let you link from an element in an artboard to another artboard. Definitely take a look at the Sketch docs for more info.
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We use Invision and haven't taken the time to explore some of the newer prototyping features but I think you can accomplish what you want with Sketch now. https://sketchapp.com/docs/prototyping/fixed-elements
apparently there's some plugin you need to download to run on your existing sketch files to 'fix' the ghost images. that seems to be hit or miss too, though.
https://sketchapp.com/support/troubleshooting/gamma-fix-high-sierra
If you are already used to adobe programs, the only thing that took me a bit is that there is not distinct selection tool in sketch. Other than that, I would say its just other shortcuts ... but they are fairly easy to remember once you get going.
This might also be helpful. https://sketchapp.com/learn/documentation/shortcuts/shortcuts/