The couple appeared Tuesday on "Good Morning America" and Shallcross dished on why Biggar was the one for him, saying "there was always something very special" about her from the beginning and she was always "top of my mind" throughout the journey.
For Shallcross to choose Biggar in the end, however, that meant he had to say goodbye to every other contestant -- including finalist Gabi Elnicki.
"It's very difficult and your mind's running a million miles an hour and you're trying to rationalize everything and then you just kind of let it go and feel," Shallcross said of narrowing down the ladies until he found his future wife.
Since their engagement during filming, the couple said they'd secretly met up "quite a bit" and did so thanks to Shallcross wearing a disguise: a fake mustache.
"I think we're just looking forward to going to a restaurant, being a normal couple," Biggar said.
With them both living in Austin, Biggar said they plan to "move in together in the summer" and truly begin their life together.
As far as a wedding, Biggar said that will come a little further down the road.
"Not right away. I think our whole relationship has just been, like, pedal to the metal, so we're just gonna to take a step back," Biggar said. "Probably in the next, like, two years we can foresee a wedding and we've talked about it so, yeah, we're excited."
Shallcross' journey as the Bachelor concluded on Monday night with an engagement to Biggar.
"I can no longer say I'm falling in love with you because ... I am so in love with you. You are my world," he said in the episode. "The love I feel from you is something I could've never imagined and something I thought a lot of my life I would never be able to deserve. I love you so much. I love you with all my heart."
Shallcross called Biggar "my world" and "my best friend."
The episode also featured one of the most gut-wrenching breakups in "Bachelor" history, when Shallcross confessed to Elnicki that "knowing you and falling in love with you has made me a better man, but..."
"I don't want to hear it," a tearful Elnicki said, repeatedly asking Shallcross to "stop" talking. "You've known," she repeated, later saying Shallcross had strung her along.
"The Bachelorette" season 20, featuring Charity Lawson, premieres Monday, June 26 at 9 p.m. ET on ABC.