The trouble is one persons remedy is another persons poison, pardon the analogy. Whichever way the team decide to go there will always be opposition (to its implementation one way or another). So compromise is sometimes required. Thus the product, Wappler, has been built and established with full community input and suggestions in mind, without swaying too far one side or the other. Very difficult territory to tread. And they do an amazing job of balancing things, although it may not seem like it to new users sometimes. I understand your point and it is valid but there are a thousand other valid points to ingest as well, the outcome is Wappler. With 4.0 many changes are on the way. Some most likely unannounced, but all will be continually improved based upon feedback from all the users in the community. Its just very difficult to please all the people all the time… But one thing you can rely on is that your feedback will be valuable none the less, and may or may not lead to improvements, and implementation in to Wappler itself.
The app structure panel provides the options which are Included in the selected app design framework. For example - Bootstrap, it has predefined classes of .m-1, .m-2… .m-5 which control the margins of the elements.
In the design panel, you define your own rules and styles. So you can set a class of .my-class and assign to it margin-top: 123px.
https://www.w3schools.com/css/css_margin.asp
Thanks Teodor. So I was right in my interpreation. Now we just need to label these descriptively in the UI, as I suggested above, taking into account the comments above from Dave et al 
This issue (pages on previewing in browser not appear to be CSS aware) has resurfaced. I had to start a project over again due to other bugs and encountered this issue again.
Configuration:
M1 MacBook Pro. Docker (Local) Node JS using Maria DB. Deployed and system check fine. On trying to preview a content page in browser, the page does not appear as designed. It has a layout attached to it. As @mebeingken said above, Content Pages do load in browser and show their contents plus any elements on the layout page assigned to them.
This seems to be a bug affecting this particular configuration. I will raise a bug report - but it is disappointing that some four weeks on, I seem to be stuck on something basic 
I have read pretty much all the documentation, understand the concepts etc. but I am not able to progress due to this.