Charlotta's place is amazing! It's super cute and was perfect for my solo getaway to Stockholm. It's a quick walk from Stockholm Central Station and I felt very safe walking alone. The entrance is very well lit and check-in was incredibly easy. Right around the corner from the Nobel Prize Museum, a quick walk to the Royal Palace/art museums/tourist attractions. I walked everywhere with no issues. There are grocery places nearby within (you guessed it) walking distance!
I would avoid roller bags as nearly every street/sidewalk is cobblestone. I used a pack and a side bag with no issues.