If you have room on the back seat then just use a roll bag. If it's for clothes only, then I would also use some stuff sacks to keep the various items separate & easy to select.
If it's your first tour you won't need as much as you may think you need. A few changes of underwear/base layers & any other 'biking' clothes you normally wear. For evenings a couple of 'T' shirts, maybe a spare fleece, trousers/shorts & shoes.
If you leave your top box on you don't have to load it, but it is handy for spare gloves, waterproofs, phone/camera, bottles of water etc.
In my case I have hard panniers, a top box & a pillion. The only time I ever notice any sort of weight is when I'm stationary. Moving & it's the same bike as when I'm on my own, without the luggage.