How long are you going for? Are you on a budget for your luggage? With a pillion or solo?
Lockable, hard luggage is a godsend, because it's easy on and off (when you leave/arrive at your hotel) and can be left securely on the bike when you go off walking or exploring.
The alternative is soft luggage and side panniers - cheap at about £40, but a pain to on/off load and not secure if you plan to leave your bike and luggage unattended.
Personally, If I was traveling solo for a week or less in warm July, I would travel with superlight minimalist clothes and just a 40 -50 Litre topbox only.
With a pillion, in colder weather or for 10days+, I'll reluctantly add on the soft panniers also.
Best advice I ever had about touring was to make 2 piles:
Pile 1) Stuff you'll definitely need,
Pile 2) Stuff you might need
Take with you half of Pile 1 and none of Pile 2. The bike rides better and it's so much easier un/packing and un/loading the bike every day.
Where are you going? a lot of people on here tour France.