a ditto on those opinions on racks. I did my loaded tours (front back racks) with middle priced racks. Do note that a rear rack with three vertical "stays" is generally better than those with 2. My 3 stay rack was not the cheapest, nor most expensive, and I had a lowrider front rack with smallish front bags that I usually put clothes and stuff in , so they wouldnt be too heavy. Had a handlebar bag too so preferred to keep the weight up front down--dont like how the steering is with too much weight up front. My total weight on month long trips, 1600km was probably in the 40-45 range (never did weigh it all, so dont have an exact number)
obviously you dont want to go with a cheap rack that will either break or flex with the weight on it.
I would however be sure that your wheels and hubs are really made for touring, and that a good experienced wheel mechanic makes sure that the spokes are all tensioned properly-IMO this is a very important thing, in all my trips, I never once broke a spoke, and in fact that same bike was used for all kinds of city commuting as well as touring and over 15 years, the wheels never broke a spoke.
I highly recommend Ortlieb panniers, the ones that you roll close the tops. Waterproof, and the nice advantage over zippered bags is that at the end of a day, when buying bulky food for supper/breakfast, its handy to be able to unroll the bags and stuff things in willy nilly and even if it doesnt fit in perfectly, you can close the bags with the clips and ride with stuff sticking out of the pannier (obviously if not raining and not for long long rides)
Ortliebs are a bit expensive, but taken care of, like I have with mine, they will last and last and last. Mine are 17-18 yrs old, with lots of commuting years also and still are very useable. I suspect there are other waterproof brands out there that are of good quality, when I bought mine, Ortlieb were the only "roll up" waterproof ones. Was so nice not to have to worry about plastic bagged clothes getting wet with rain.
ps, my front panniers were not Ortliebs nor waterproof.
I fully second the opinion of doing some weekend trips to see how the bikes handle loaded, and to figure out over time what stuff you need, stuff you dont need etc. I would really urge you NOT to leave this all to the last minute, as the person said above somewhere, a short trip really does give a good idea of needs etc cmpared to a long long trip.
and yes, use the internet like crazy to see routes, and help with route planning and expectations for distances between towns, water, food, less busy routes (like how to avoid a busy with lumber truck type of road)
all the best,