North Wales 2 week trip without a car

Hello, I'm interested in visiting Wales for a couple of weeks during summer (solo female traveler). Will be visiting from US. Not comfortable with driving as per UK rules yet. So, wondering if it would be worthwhile traveling either North or South Wales just by using public transportation (which one is better) (or) any suggestions for group tours? Preference is visit more castles and scenery.

Or should I opt into driving and get familiar with it to get a better experience?