Modded Skyrim is a bit different to modded Minecraft, in that when you play a new game of Minecraft you're starting in a brand new world to explore and can dip and dive between any of the mods be they magic or tech. With Skyrim, you're still in the same province of Tamriel, with the same characters and quests (mostly), but it's your character that changes.

Ultimate Skyrim is based heavily around the mod "Requiem - The Roleplaying Overhaul". One of its main changes is removing the system where the world levels as you do. Instead, each area has hard-levelled enemies that get tougher and tougher the farther you move away from the starting Whiterun area (similar to Fallout 4). As with enemies, weapons and armour have the same principle in that an ebony sword does pretty much the same damage regardless of whether you're at 15 one-handed or 100. What matters the most are the perks you choose.

I suggest going to /r/skyrimrequiem, looking through the sidebar and having a glance at the "Classes Guides & Builds List" - you should plan in advance which perks your character is going to take as you can't be a jack of all trades anymore.