Played Witcher 3 with both expansions when they were just released.
Started my 2nd playthrough this year, just completed first dlc yesterday.
It is a masterpiece, and expansions are even better than the main game in my opinion. The story, the side quests, the combat (play on "Blood and Broken bones" difficulty), the music.
Just don't rush it and enjoy, and explore, and immerse, read the bestiary, brew your potions and apply oils on blades. The story does start a bit slow but I think it was meant that way. It becomes much more intense later.
About the difficulty. There're 4 levels: easy, normal, harder, hard.
Choose the "harder" (Blood and Broken bones), anything easier and you will not need neither alchemy, nor oils, and won't need to prepare for the hard fights (witcher contracts). They meant to be a bit harder than your normal pack of wolves. And alchemy is a big part of Witcher lore.
If you're afraid of dying, then invest points into the active shield that regenerates health when you take damage. It will save you a lot.
On easy difficulty levels you can kill everybody with pressing just 1 button. It will become boring.