This mod will allow you to spawn spawners in the world so you don't have to find a location with the spawners already in it. This way you can build where you want and have the creatures you want around.

EasySpawner
https://www.nexusmods.com/valheim/mods/374

hostiles do not spawn within radius of a workbench. thats the only way to stop spawns, other than to dig down to the water

I love the concept of using a game as a screen saver. I do it frequently with a few games. Besides Valheim, there is Dyson Sphere Program which makes an amazing screen saver.

No Mans Sky is always a good one, too.

Yes there are specific spawn points for specific creatures.
https://valheim.fandom.com/wiki/Spawn_points
Not listed are spawn points for neck, deer, and birds which are always the same. Neck spawn points occur near water in the meadows. Deer and birds can (rarely) spawn even if the spawn point is inside the range of a workbench. This may be a bug or may be intended since birds and deer can't do damage.
https://steamcommunity.com/sharedfiles/filedetails/?id=2860289081
https://steamcommunity.com/sharedfiles/filedetails/?id=2920176358
https://steamcommunity.com/sharedfiles/filedetails/?id=2924127097

1 & 2 no, stuff will still spawn. I am not sure spawns are entirely tied to 'points' so much as 'put a grey dwarf out of LOS near player every 3 seconds' type logic.

3, the spawners are special things. They are physical 'buildings' that you can destroy that spawn the monsters. Again, the normal spawn is simply to create the monsters out of LOS near the player.

4. you can summon the spawn buildings for those specific enemy. And you can summon specific entities, like a troll. I don't know the codes.

note that workbenches, fires, and some other logic prevent spawning 'near' player structures, so building a castle will likely break spawns near it, to some distance. You can read the wiki on that ... there are a lot of details because most players want to keep monsters away.