The 2013 Capital One Cup winners have added five new players since the end of last season, with Wilfried Bony, Jose Canas, Jordi Amat, Alejandro Pozuelo and Jonjo Shelvey all moving to the Liberty Stadium.
Dutch international Jonathan de Guzman returns for a second season-long loan to further bolster the options for the Swans' Danish manager.
With Swansea winning just twice in the Premier League after their League Cup triumph over Bradford City, strengthening the squad has pleased Williams, who was recently confirmed as team captain in succession to Garry Monk.
"It's just what we needed," said Williams. "I think we've got two players for every position when everyone is fit, and that is the competition you need.
"We have that strength now that means when you do want to make a change or you have to change it because of injury, the side does not get weakened.
"Look at the left-backs we have now and the options in central midfield - I'm glad I don't have to pick the team."
Williams added: "The selection calls are nice problems for the gaffer to have.
"It's good for us as a team and exactly what we needed because since I've been here, I have always thought we've had a light squad and that we struggle sometimes when players who are regular starters are out with injuries or suspensions."