Tough means a hefty col at least every other day;
Not so tough - one or two cols over a week;
Bit hilly here and there - hills rather than mountains;
Flat, more or less - the only elevation is a step into a café or two.
Tough
Geneva - Aosta - Provence 444 miles
Geneva - Vars - la Bonnette - Nice 350 miles
Annecy - Galibier - Agnel - Nice 302 miles
Not so tough
Toulouse - Marseilles (Cevennes and Ventoux) 417 miles
Malaga - El Chorro - Ronda - Malaga 168 miles
Malaga - El Chorro - Ronda - Malaga 168 miles
Calais - Dieppe 217 miles
Dieppe - Dunkerque 142 miles
Dieppe - Albert - Serre Rd - Somme - Calais 196 miles
Givet - Luxembourg - Semois - Meuse - Givet 230 miles
Dieppe - Bayeux - Beaches - Ouistreham 210 miles
Dieppe - Paris - Dieppe 160 miles
Flat, more or less.
Dieppe - Dunkerque 142 miles
Dieppe - Albert - Serre Rd - Somme - Calais 196 miles
Givet - Luxembourg - Semois - Meuse - Givet 230 miles
Dieppe - Bayeux - Beaches - Ouistreham 210 miles
Dieppe - Paris - Dieppe 160 miles
Flat, more or less.