France, Portugal, Spain

"starts in Calais or Honfluer" - a strange pair of starting points. How are you getting there?
Honfleur has no rail or ferry connection I know of.
Calais has ferries from Dover, but If you are coming from London by train there are more trains to Lille.

You are going through many areas which could eat up 1-2 weeks each, Normandy, Loire valley, Aquitaine, Basque country, Pyrenees, Catalonia, Midi, Burgundy to name a few. There are many lovely places to visit in each, I think you need to acquire a Guide book for each region (library, second hand book shop) and do a lot of reading.

If you are following the coast of France, then this is a car tour. Picking up a car in France it needs to be returned in France, if you do that at Charles de Gaulle airport that is OK.
For routes, times and costs I recommend: https://www.viamichelin.com/ The times it gives assume no stops for anything, so add 25%. Costs shown are fuel and tolls (Autoroutes/autopistas). There is a "avoid motorways" option which routes you avoiding the Autoroutes/autopistas.
Autoroutes are OK for getting from A to B, if you want to see the sights and visit towns you need to get off the autoroutes. "A61, or A75, or A9" - none are good for sightseeing EXCEPT the famous Millau viaduct on the A75 (photo: https://upload.wikimedia.org/wikipedia/commons/e/ed/Creissels_et_Viaduct_de_Millau.jpg )

Going all the way to Portugal is a long long way. According to ViaMichelin:
Time: 19h27, Distance: 2018 km including 1977 km on motorways Costs: €298.43 including Toll €133.85, Consumption €164.58
If you tick the "no motorways box you get:
Time: 36h52, Distance: 2202 km Costs: Consumption €203.28
A lot of driving. You may end up just getting as far as northern Spain.

"We love city centers where we can walk the sights, and balconies overlooking the sea." - If this is a car trip, it will be rural and towns only, no big cities.

Poops, just recalculated the distance. I screwed it up the first time. I need to rethink our next trip.
Tha,nd.

We have been to several places along your planned route.

Normandy-- Don't miss the WWII beaches, like Omaha, Gold, etc. Go to Bayeux and see the amazing Bayeux Tapestry that tells the history of the Norman Invasion of England in 1066. It is over 900 years old and in fantastic condition.

Lots of WWII history in Normandy. Also, I suggest Mt. St. Michel on the border of Normandy and Brittany.

Not sure if you want to go inland much, but the Loire Valley in France is worth a few days. We stayed in Blois.

Farther down the coast, Bordeaux is one place we want to visit in the next few years. Continue down to the Basque region, and into Spain, San Sebastian and Bilbao.

Then head over to Galacia (Spain) and don't miss Santiago de Compostela. Then past Vigo and down into Spain. There are interesting places to stop on your way to Porto.

For Porto, I recommend a full day exploring the city (try some Port wine), also consider a river cruise or taking the train into the Douro Valley, it is wonderful. The Bed and Breakfast, InPatio Guesthouse is wonderful. It only has five rooms so book early. Location is great.

Down the Portuguese coast there are lots of choices, I suggest purchasing a Rick Steves Portugal Guide (also one for France and Spain). Don't miss Cascais, Sintra and Obidos. Head over to Lisbon and spend about three days there. Not sure if you want to see the beaches in the Algarve, but if not head east toward Spain and don't miss Evora with its Roman history.

In Spain, the gem of Andalusia is Seville. Spend at least three days there, also see Cordoba. If interested in Morocco, you could take a day trip from Malaga or if not head up to Granada to see the Alhambra. Then up to Cartagena and Valencia before you reach Barcelona. Spend 3-4 days minimum there with a day trip to Monserratt.

On your way back to Paris, you could see the Carcassonne region of France.

I presume you rent a car. Make sure you have a good GPS or Nav system. We did a four week drive tour of Wales and England last year and it is essential in finding your destinations, especially in the cities.

Hi,
If you have the time this Road trip will be epic.
I would suggest you look at RS videos/books, however I would strongly suggest you get the Michelin Green Guides. They are much better for driving and looking for good routes and best lookouts. At the very least get the Michelin road map for the area that also routes scenic drives.
We did a 4 wk. road tour of just Portugal, across the northern part of Spain and into S. France.