Randomly recruited (through beacon) settlers can be ghoul, but they're rare. Still, you can get as many ghouls as you want if you sift through enough random settlers. You can also use your companions as settlers to some extent and there is a recruitable robot settler (Buddy) out there if you don't turn him in for a certain quest. If you decline to finish Curie's questline (but definitely do her quest anyway, because she's awesome), that'd give you 3 robots between her, Buddy, and Codsworth...4 if you count Nick maybe. Strong is your resident supermutant. I do wish we could find/build more robots. Robot hacking skill should let us claim robots we find around the world for our settlements. Protecterons, Assaultrons, Handies, Gutsies, and Sentries! Maybe even some Gen 1/2 synths. I'm sure mods will deliver.
Settlers are fine once assigned. Sometimes settlements need defense or radiant quests to be completed though... is that what you're talking about? Jack up your defense to 2x the food+water count and you'll rarely get attacked. Don't turn in the radiant quests after completing them (ie, hold the last 'turn in to preston' stage) and it will drastically slow down radiant quest generation.
Wish we had that...yeah. The best you can do now is dress your settlers by job so you can see at a glance what each is doing. Under resources->misc there is bell you can ring to summon all the town's settlers (except provisioners that are away). It doesn't always summon all the settlers though for some reason... but it helps for finding unassigned settlers usually. I wish we had a better way.
Mods have already solved that for me. I think it makes sense for Bethesda to focus on DLC at this point and let mods handle the mountains of extras.
Massive stockpiles of valuable purified water that you can sell and rows of shops are a pretty good reward for settlement building. The big reward though is looking at the massive towns you built and thinking, "I made that happen!". Not to mention, settlements fuel the reinforcement calls for Minutemen help if you bother to use that (I never bothered) and an artillery network provides some very extraordinary destruction when you want it (I love the fireworks!).
I was overwhelmed with the huge number of settlements the game throws at you so fast, but I've warmed up to the concept now. It gives you options. Some you'll love, some you'll hate. Options are good and you aren't obligated to develop them all. For those of us that enjoy building, it gives us more variety in the late game, which I've come to appreciate. I can do fun stuff like have a beach resort town, a scrapper town, a trade hub, a water purifying town, ect. The big reason we get so many settlements though I think is the very conservative object limits. You can't build a massive city normally, and such a thing would drive some systems to crashing and serious framerate drops. Those of us with decent machines learn to bypass the limit...but it makes sense to provide a lot of settlements so that people stuck with the default object counts can continue building.... just not all in one area.
I'm not sure what you mean... I've built my own base at Red Rocket. For a long while, I had no settlers so everything there was mine. Now I have a few settler guards and a few settlers in red rocket mechanic jump suits that go around pretending to work on my rows of power armor. I have a private penthouse that overlooks the area. That is mine. It's mine because I say it is, and who's going to argue with that? I've got the Minutemen and enough firepower to obliterate anyone that tries to take it... of course, that isn't likely to happen, and if the settlement gets attacked, the enemies will be wiped out by rocket turrets while I watch from my high tower.
Do you want to micromanage junk? I don't.
I think the construction interface is pretty good overall. If you compare it to similarly ambitious systems in other games, Fallout 4 actually comes off as polished and use friendly...albit overly simple at times. It is difficult to great freedom of construction AND be simple and polished. If you want the full power of a level editor, you end up with an interface like a level editor, and not many players have the patience to learn what amounts to a glorified CAD program. I wish they'd allow clipping, since a lot of the placement restrictions don't seem to make sense and you might as well let the player decide if something belongs there or not. We definitely could use some more settler management UI. There are some nastier bugs, like sparks that you can't get rid of if you accidentally leave a hanging wire and save the game (I have one eternal spark like that...). Hopefully some of that will get patched. Mods will help in other areas. If you learn console commands (GG Console players) you can precisely move objects where you want them.