Welcome to the forum !
I'm not an expert by any means, but I've fired the PP, PP Super and I own a PPK/S now. But I'll try to answer your questions as best I can.
1. These are very fine weapons, indeed, with an almost 80-year history. They were used as police sidearms for years, and were only recently supplanted by lighter, smaller compacts as back-up guns (BUGs). All of the PP line is heavy for its size, based on the all-metal frame. There exist today a wide variety of polymer-based alternatives that are much lighter and probably as reliable. They are extremely accurate, and were the best I've ever shot with a pistol out of the box. It's a very pretty gun, and of course the PPK-type has the James Bond appeal.
2. Cleaning is easy. Blowback designed pistols (and SMGs) leave residue in very predictable places. PPK's strip very fast- you could accomplish it in 10 seconds easy. A more detailed strip is simple, and reassembly would require little effort or tools. All-metal frame and slide (as well as most internal parts) will require more lubrication, but will also last longer, and stand up to harsh cleaners more durably.
3. I purchased my PPK/S in .380ACP, but purchased slide, magazines, and barrel for .32ACP. I've done the conversion a few times now, and shot both as much as I could. The .380 has an extremely powerful recoil, that is not fully absorbed by the frame of the pistol, so the remainder will go into your hand. After 3 magazines, the skin on the webbing of my hand was broken and starting to bleed- not from slide bite either. .380 was very accurate, and 4 ammo types fed well, with only minor feed problems when I was breaking in the pistol. The .32 was smooth, fed very well, and was just as accurate. Muzzle flip was strong still, due to the very short barrel, but recoil was very manageable. Ammo was fine. You'll find most newer PPK(/S)'s sold in the United States today to be .380, because it's a larger, more powerful modern ammunition, respected for "stopping power". As a target shooter, you can't go wrong with either one.