Your plan is very doable. I did two 800 mile solo tours with just one night each in a motel with just a large English saddlebag, handlebar bag and a rear rack. Handling was poor but I didn't know any different.
But - I now load heavy stuff in the small Ortleibs on LowRiders before everything else. What an improvement in the ride! I haven't toured for many years but I have two bikes I use as workhorses and am very familiar with loaded bikes. When it comes to bike handling, weight, even large amounts, in LowRider panniers is "free". Oh yea, you still gotta lug it uphill but you can get out of the saddle, rock the bike just like it was unloaded. (The weight also steadies the steering and makes things like angled railroad tracks far safer - as long as your front wheel is sufficiently strong; that weight is far harder on rims than any place else on the bike. Use a big enough tire! In my Ann Arbor school days I used to bring hardcover texts I didn't need into campus for bike control climbing the snowy/icy ascent out of my complex and safety for the hill into campus. Big help on the RR tracks in winter.) The further back you get the weight and the higher it is, the more it affects the feel of the bike (and you ability to stand for hills or just to get out of the seat easily).