Having thru-hiked the AT, backpacked and bike toured for many years I find two major differences. A place to pitch your tent is much easier to come by on the AT than on the road in my experience. When you run out of gas on the AT you find the nearest water source and camp. On the road, especially on the coasts, that can be a bit of a challenge. Be prepared to ride after dark if you get a late start or overestimate your ability to reach your destination. Things like rain, headwinds, traffic, heat, and hills hit you a lot harder on a bike than hiking. It is a lot easier to go 50% slower than planned on a bike than on foot. I like to have a plan A and plan B destination. Hiking I always plan for a 15 mile day and recalculate over lunch. Especially with a group, you want a midday rally point since a touring group or a hiking group often travel miles without seeing one another. Bike travel planning for me seems to have many more variables. I find it is easy to over plan or under plan my mileage. If you have the guts to ride with no plan and see what happens that will set you free.
Darren Alff
https://www.darrenalff.com/ who calls himself the bicycling touring pro has some great videos on roadside stealth camping I watched them on YouTube. We have so many darn reflectors on our bikes and tent lines now, we light up like a pinball machine if not out of the reach of headlights at night.
Resupply is thought of in terms of days on the AT but in hours while bike touring. Your water supply is the next stream, spring, etc on the AT and typically the next gas station on the road. You can live without food, but water is a keen necessity. Just like in times of drought on the AT, water sources guaranteed on the map are often dry, in times of COVID water and food sources on the map may be closed, closed on a particular day, etc. Especially with the staffing issues many small business are having when the government is paying more to not work. Bottom line - always carry a spare meal even if it is ramen or a freeze dried meal and never pass up the opportunity to top off your water. You know you are sweating when backpacking as it runs in your eyes, but the breeze on a bike quickly evaporates sweat, so you need to consciously hydrate if you are new to the transition between sports.