Rakes and sickle mowers take pretty much no power or tractor weight to run. About the only issue you might run into is the really small tractors don't have much ground clearance and they might not do very well wading through uncut hay when cutting, or going over the cut swath when raking.
The main issue with running a small square baler with a very small tractor is that the tractor won't weigh very much. The tractor needs enough traction to keep the baler from pushing it around, especially if there are any hills. A typical "newer" (mid-1960s and later) small square baler weighs between about 3000 and 4500 pounds, and in general it is recommended that the tractor needs to be heavier than the baler in order for the baler not to push it around. One might need even more weight if the tractor has tires that give it less traction than regular ag tires. And that weight recommendation is for if you just pull the baler behind the tractor and drop the bales on the ground. You would need even more weight to handle a bale wagon/bale basket/accumulator behind the baler. You also wouldn't want to run a baler with too light of a tractor even on flat ground as the baler would shake the tractor back and forth pretty uncomfortably as it packs bales.
Putting up loose hay could be done with a minimum of equipment, back in the past it was done with at most a horse or two. Sickle cutters, rakes, and hay wagons take little power to pull. The real work came in forking the hay into the wagon and then getting it out of the wagon into the barn, and much of that was done by hand. That makes throwing small square bales look easy by comparison.
I don't envy you trying to bale with a 30" baler pickup. You are not kidding about needing to control windrow size when raking if that's what you are needing to do. I would absolutely want no part of a wheel rake with trying to make a windrow that's less than 2 1/2' wide. I bet that it might be tricky to get it narrow enough even with a bar rake if you are in a good stand of hay. I do wholeheartedly agree that a good bar rake is much easier to use in a smaller and irregularly-shaped field than a wheel rake, and it is much easier to control windrow size and shape with one vs. a wheel rake- particularly a V wheel rake.
I would say a small square baler is easier to bale with than a large round baler, I have never used a little round baler. From what you describe, the mechanisms appear pretty similar between the large and small ones. With a small square baler, once you have set the baler set up, all you have to do to keep the windrow between the edges of the pickup and just keep driving until you are done. This compares to watching the bale shape on the monitor and weaving across the windrow to "fill in the low spot" in the bale if needed, watching the bale size closely so you can stop when it's at the correct size, stopping when the bale reaches the correct size, either having to activate the tie or wrap mechanism or have stopped just at the right time so the computer can activate it (and if you forget to stop on an auto-tie/auto-wrap baler, fixing the big mess you made by continuing to bale when it was trying to tie or wrap the bale), waiting for the bale to tie or wrap, ejecting the bale and making sure it doesn't roll somewhere it shouldn't when you eject it, and then resuming baling. The real hassle with small squares versus large rounds is in handling and storing the small square bales, not in baling them or maintaining the baler.
There are certainly a lot more zerks to grease on a small square baler than a round baler. However, round balers are every bit as needing of maintenance as it is much more critical that their bearings get greased well and the baler gets cleaned well compared to a small square baler. A bunch of debris rubbing the belts in a round baler or a bearing going bad can cause a fire that burns the baler to the ground. There is a reason that many new round balers are sold with a big 'ol fire extinguisher strapped to them, while small square balers are not. Knotters are the "fun to fix" part on a square baler, sensors and belts are the fun to fix parts on a round baler. My experience is that both types are quite reliable if maintained properly and stored inside.
