Best route through Wales

Steve138

Hi, I'm staying on a site near Tenby in Pembrokeshire in mid August then moving on to Porthmadog.  I'm towing my caravan and am trying to decide which route to take.

The A40, A487, A470 up the coast looks the shortest route (on main roads) but what's it like with a caravan on tow? Is there a better route?

This will be our first real tow on roads I've not driven before so any advice would be welcome.