Is Query Slower When There Are More Columns in one Table?
I have a related blog post here: Do You Have Tables In Your Tables? that I'm going to quote a bit from.


  What Makes Them (wide tables) Bad? 
  
  They’re nearly impossible to index
  efficiently:
  
  
  Queries will hit them in many different ways 
  WHERE clauses will be
  unpredictable 
  SELECT lists will vary wildly 
  
  
  When indexes pile up to support all these different queries, locking and blocking will start to become larger issues.


Other things you may need to consider: 


LOB data (MAX columns, etc.)
Query Memory Grants
Modification concurrency


Putting everything in one table sounds like a bad idea. If users are allowed to change any information related to a profile that you've listed (name, telephone, personal information, etc.), those queries are now competing to locate and modify rows alongside your app tracking login information.

It's a recipe for bad blocking and deadlocks down the road. 

The "one big table" approach sounds quite convenient at first, but the convenience early on will never surpass the inconvenience you face later of needing to split the table up into a proper schema.