Getting started with SharePoint Online template development

Hey team,

I am hoping someone might be able to confirm a few things for me and point in the right direction of where to start.

We are currently looking at migrating/rebuilding our knowledge base online and integrating it into a homepage type format as well. I have attached a mockup of what I am roughly wanting to do but the documentation is very hard to follow to even confirm if it is possible and where I start.

I am hoping to be able to use one of these templates as a base https://spdesign.azurewebsites.net and use Microsoft's tool to get them into our tenant. https://techcommunity.microsoft.com/t5/Microsoft-SharePoint-Blog/Take-advantage-of-the-SharePoint-Look-Book-sample-designs-in/ba-p/465919

Where I come unstuck is confirming if I can build our pages/sites exactly like in my mockup using those templates as a base ( or at all ) and how do I go about it. Our main focus is to have everything in this new knowledge base search driven NOT menu driven, hence cleaning all the header stuff away and having a great big search bar in at the top. All of the 2nd tier menu I want gone. No header, no following icons, no how many members, no menus or edit buttons, no commenting etc etc.

Any starting point would be good.

Thanks