Best Driving Route Through Wales To Caernarfon?

That's quite a drive to do in one fell swoop. I'd be astonished if it could really be done in just 5 hours.

Whether or not it is worth is completely subjective, and your decision alone, but if it were me - I'd want to stop and look at things and visit along the way, not just get there the fastest possible. You are talking about the full length of Wales, a land of valleys and gorgeous mountains.

I guess I should have elaborated; we will stop on the way, just mentioned it was a 5 hour drive. Any recommendations of which little village to stop in?
Thanks,
Jean

Can’t help much since we drove the coastal routes to get to Caernarfon. If you do drive that route, I’d be interested to know what interesting places you stopped at en route.

In passing both Bishops Castle and Montgomery are cute places at least for a tea break.
The Andrew Logan Mus. is near Montgomery..quirky indeed

Llanidloes and Machynlleth are interesting towns
I was going to plug the Star Inn up in the wildness at Dylife but sadly looked like it's closed this year

Sister lived near Church Stoke and I saw in 2000 from the castle walls above the square in Montgomery

We drove from Caernarfon to Wiltshire over a number of days. Our route took us through Llanberis (so I could run up Snowdon). To Harlech, lovely place great castle lovely beaches nearby.
To Rhayader, a handsome little town. To Crickhowell, cute as a button (we had previously done a wonderful hike there and camped overnight). To Abergavenny good sized interesting town fascinating history with the castle. Then through Raglan, a magnificent 15th C castle.
That's not exactly the route you are taking but the driving we did was fantastically scenic.
We stopped frequently in villages and small towns for snacks and walks. I remember having a wonderful lunch in a hotel in the handsome good sized town of Brecon.
Caernarfon Castle was far and away the best Castle I have visited. Nice town too.

i would suggest you leave Bath - go N to M4 and then cross into Wales on the M48 bridge and come off at first junction on Welsh side. A466 to TINTERN ABBEY (ruin). A466 to Monmouth & then A40 west to RAGLAN CASTLE (ruin). You need to loop around at Raglan so be careful and re-join A40 westbound for ABERGAVENNY. Then A40 via CRICKHOWELL & branch R to A479 towards Talgarth - which you by-pass.

Then A470 via Builth Wells, Rhayader, Llanidloes (worth a look). At Caersws turn L still A470 and head to DOLGELLAU. From here you can follow the A470 (faster) north to Snowdonia but I would suggest that you take the scenic (& slow) A496 via BARMOUTH & HARLECH (Castle) to PORTHMADOG. (PORTMEIRION ITALIAN STYLE VILLAGE IS IN THIS AREA).

Go on Google Maps and try and find the route. Look at street view to see the type of roads. Also look carefully at junctions by zooming down so you are aware of what you will encounter. This is especially important if visiting Raglan Castle.