I just answered a question about cycling in the Loire and Dordogne so I'm going to give you a link to that thread instead of repeating myself. What I will say is that all of your questions should be answered once you look at the freewheelingfrance and loirebybike websites:
https://community.ricksteves.com/travel-forum/france/advice-please-bicycling-loire-valley-seeing-sarlat-perigord-without-a-car
I'm sure you are looking for specific recommendations and I hope folks who have specific recommendations will provide you with them but in the meantime here are just a few websites for companies offering self-guided bike tours in the Loire:
https://www.levelovoyageur.com/en/loire-valley-cycling_d12
https://www.loirelifecycling.com/self-guided-loire-valley-cycling-tours/
https://www.cycleeurope.com/self-guided-bike-tours-europe/france/best-cycling-loire-valley/
https://www.cyclomundo.com/region/normandy-5.html
https://www.utracks.com/France/Self-Guided-Cycling/Loire-Valley-Cycle
With all that being said, all you have mentioned about your itinerary is cycling between Tours and Blois and you haven't mentioned how many days you'll be spending in the region or if there are other routes you'd like to cycle. If all you want to do is cycle between Tours and Blois then there is no need to spend the money for a self guided tour as this is something you can easily do on your own and in this case just look at the freewheelingfrance and loirebybike websites and everything you need to know is there. It's an easy and flat route along the Loire river between these two places and there are endless places where you can spend the night (or more than one night) anywhere along the route. Using the two websites I mentioned you'll also find info about companies that will transfer your luggage. See the tourist office websites for any place you might want to spend the night or just use google. For example, here is the tourist office website for Amboise:
https://www.amboise-valdeloire.com/