Indeed, the A470 is a super route. The biggest challenge you will encounter is the long incline near Dinas Mawddwy pronounced Dinas Mowthree (Dad's Welsh, lives in Harlech, Gwynedd).
However, if you want a motorway route from Swansea, take the M4, join the M5 and then the M6. Leave the M6 at Junction 16 and follow signs for Nantwich and then Chester on the A51 (Nice open road) and then join the A55 which will take you to Colwyn Bay.
I live in Uttoxeter, Staffs. I travelled down to Herbrandston near Milford Haven, Pembrokeshire in 2020 and debated for ages on the best route, finally choosing the M6, M5, M4 major routes. Longer and by far less scenic but definitely more relaxed and fuel efficient.