I'll echo what most are saying. PTO speed is based on transmission gear selection and throttle on the 8N/Jubilee family, making PTO speed relative to ground speed because the same shaft that drives the rear wheels drives the PTO. Unless you find a way to speed up that PTO or slow down the tractor, a tiller probably isn't going to work well. A disk should be sufficient for annual tilling. Make sure it's wider than the tractor so that you don't leave tracks. A turning plow of some sort will do you justice every 3rd year or so, depending on your soil. If it packs (clay) you may have to turn it every year until you get enough humus and sand mixed in to make it ideal for growing veggies. You're going to find that topsoil under grass usually isn't very deep. Hopefully the subsoil is sandy loam. Disk it as deep as you can. You want loose soil at least 8 inches deep for growing veggies. If you're going to keep any of the hay fields, you're going to want a fertilizer spreader of some ilk, a hay mower (completely different from a grass cutter). I highly recommend a sub-soiler (AKA chisel) for drainage and trenching use, as well as a middle buster (AKA furrower). The sub-soiler can be used to cut deep trenches in the soil to allow water to run off below the surface and help control erosion and soggy spots. The middle buster is great for adding a ditch, or better yet, no better way to dig up potatoes unless you get a specialty tater digger. Not sure you'll find that for a 8N/Jubie.
You definitely want a way to mow with it. Like another poster said, there's ALWAYs some grass to cut. A flail mower probably isn't going to work as well behind the Jube for the same reasons as the issues with the tiller. We had a sickle mower for cutting hay, and a 6' Bush Hog (rotary cutter) for pasture maintenance and brush clearing. The sickle mower worked well at lower speeds in lower gears if you kept the throttle up. Going too slow was a sure way to clog the sickle, and too fast would leave too much standing. It's a fine art cutting cleanly with a sickle. If you put a rotary cutter behind that Jube, make sure that a slip or ratchet clutch is in the drive line, and that it works. The centrifugal energy of that cutter will keep pushing that tractor, brakes be damned. I put our 8N in the creek more than once. The creek wasn't very deep (about knee deep) but going down the bank headfirst was always a thrill. No seat belt, and I'm sure I pinched a few new vent holes in that old steel seat when I realized I was headed into the creek. Who needs amusement parks and roller coasters? If it happens, kill the engine, drop the cutter all the way down, and keep the nose pointed downhill. It's going to be a rough ride, but better than rolling sideways. If my mother had ever seen it happen to me, she'd never let me get on another tractor. I never rolled one over until much later in life. I put our Cub Farmall on it's left side a few times leaning up against something, but didn't actually roll anything until my late 40s. Me and a Murray rider got too close to the edge of a ditch. Fortunately it was light enough it didn't really hurt me, but it sure made some nasty bruises and I was sore for a while. The scary part was, it came down on me with the seat switch still compressed, meaning it was still running with the dirty side up. I was very lucky.
A rear blade of some sort is also a must. A grader blade is better for heavier scraping and pushing when working new access or woods roads. A box blade will make a better finishing tool, albeit you'll probably have to make more passes. A box blade isn't designed for hogging off material. It accumulates and drags material with it to fill holes quicker, whereas a grader blade will shed material to one side if used correctly. The grader blade is better for crowning roads and cleaning ditches. The box blade is better for surface finish. I've seen folks that could do any chore with either blade. They were more talented than I.
You're obviously new at this, and some things you'll figure out for yourself or learn in the process of becoming a professional veggie farmer. The Jube is a wonderful workhorse. Think about it, it's 68 years old and still running. I don't think you can ask for better proof of reliability. An old 8N or something like it was what I wanted for clearing my lot. But the demand on them makes them hard to find in running condition, and when you do, the price is sky high. So, I got an LX2610SU instead. Like you, though, I'm still collecting implements and attachments.