One addition: If you do not plan to replay the game, you should explore very thoroughly in order not to miss several NPCs and their side quests (e.g. you can naturally meet about 10 NPCs in Limgrave alone before entering Stormveil castle). Or you search for a page listing all NPCs and their side quests, so you can check, if you have missed one.
If you want to explore a bigger dungeon before entering Stormveil Castle, go to the east in Limgrave and look for the Siofra River Well (a little bit northeast of the Mistwood Ruins).
Thanks for the recommendation. I went and explored a little bit outside of my level range, at least that's what it felt like. I even went far to the east, to the burned looking landscape with the dudes that give you scarlet rot. But quickly made my way back since it was obvious I was out of my depth. I then went south, and activated the map obelisk thingy there too. I'm not sure what the purpose was of hiding them map and only displaying after reaching those obelisks. It felt cool as a concept, but it's kinda meh in practice.
I also cleared and got access to the mage under ruins where the giant plants live (I think it's called Waypoint ruins), and picked up the weapon imbuing spell, that enhances your weapon with magic damage for 90s. And man did I need it for the fight against Margit. I also summoned the wizard right at the gate to Margit, and after around 5-6 attempts where I always ended up failing (this with 5 charges of the healing flasks at a +2 level) I was prepared to give up, and return later.
But after checking my inventory I noticed that I had found a spear that had +7, which I didn't even notice. It scaled with Dex, so at first I didn't give it much thought. This was also before having realized that the Round-table hold is only accessible via fast-travel, and I thought I was supposed to get to it only after Margit. I did see Melina's prompts at the bonfires, but thought that was just the game wanting to get me there faster, which felt weird. Anyway, the point was that I fought Margit before getting to Roundtable Hold, and before having a change to upgrade my usual weapon, a two-handed blade (I think it's called the Dismounter). So after having failed with that, since it had such a slow animation and range, I just switched to the Spear and demolished Margit (admittedly, on the second try with the spear). It seems the extra-range was enough to get me the edge over him, and I also luckily stunned Margit right as I was without anymore health charges. So I just narrowly killed him, before he killed me again.
Not sure if he's supposed to be that hard, or if I was just underleved, but it felt like a considerable challenge. Though, I was really happy I managed to best him after only 7-8 tries.
Anyway, besides the tense fight, the best thing about the game so far is the exploration. Just amazing. And I love how they hide smalled hidden holes everywhere in the castle. I love that. I hope they keep this great level design throughout the whole of it.