Personally, I build my projects in Site Designer (SD) starting at 'mobile first', and I don't use any templates. All the templates that have appeared here over the last 4-5 years have been made for the 'desktop down' approach.

It depends on how comfortable you are with the workwise of SD, whether you want to use a template or not. I've always found it easier to make sites wider as I go, instead of narrowing them down, so that is why I prefer to start at the narrow end.

If you start at the same end as I do, you just need one column to begin with. When by moving the width slider up a bit (to the right) and you discover that there is room for more elements beside each other, you set a breakpoint and divide that column into two (or more). If you get stuck at some stage, feel free to ask for help.

You appear in this forum as a 'guest', so I assume that you haven't bought the SD yet. The trial period will then soon expire.