I use a very limited method for making my website web-responsive.

I upload two index pages, one for PC, one for mobile.  Both designed to 375 pixels width.  One index.html and the duplicate m.index.html.  The rest of the pages on my site I simply build @ 375 pixel page width as m.pages.

I used to design the whole site @ 1000 pixel width for PCs, which needed people on mobiles to mess about resizing.  But this year a web designer told me that these days 95% of web traffic is on mobiles - so don't bother.  Just design the whole site at 375 width.   Anyone viewing your page on a PC or larger notebook will see the content fine, just with larger margins.

Is this correct as a strategy, does anyone think?  Because ages ago I was told (again by a web designer but someone who actually used WebPlus) that I should design the main website then duplicate each page expressly for mobile.   I could not contemplate the work involved in designing 2 entirely different layouts for each page, so I never did it.

The web responsive thing is a good reason for moving across to wordpress/wix - EXCEPT that I also don't really know how those work in terms of design.  i.e. websites where the design is a page width on my PC but it converts to a vertical layout when I pull up the same page on my mobile - I don't understand how those platforms would 'decide' what happens when the page is displayed on a mobile without you actually controlling the visuals.   I'm fairly sure wordpress/wix people aren't designing 2 layouts per page or I'd have heard about the workload by now, I reckon.

Any illumination on this would be so much appreciated.  Thanks.   Have been dithering about all this for many years.