For the multi-day touring rides that we done which most we do on our own with no sag support, admittedly I'm pretty simplistic for packing in case of rain:

I keep my "cleaner" clothes in a separate plastic bag from another bag with cycling gear. Then another bag for clothing that needs to be laundered...when I get home. Toiletries in a separte little plastic bag. My toiletries I tried to use items that were used enough at start of trip, that I would use it all up by end of trip. Travel size toothpaste sometimes just wasn't quite enough for the length of some loaded trips.

That's all. On some earlier trips, before I started to wear cycling jerseys only in past 5 years, I was ..wearing T-shirts...and would wear an older t-shirt and later on trip, throw away the T-shirt..lighten the load.