In Stockholm, one can use the same commuter card for buses, trains, boats and bikes. But where to go? If you are planning on arriving early or staying an extra day or two, to see the city you can visit the following websites for ideas and tips on activities and attractions in and around Stockholm:
https://visitsweden.com/
https://www.likealocalguide.com/stockholm
Or look at these suggestions from the New York Times:
https://www.nytimes.com/interactive/2017/07/06/travel/what-to-do-36-hours-in-stockholm-sweden.html?smid=fb-share
Stockholm has a wide variety of accomodation available. Given that the conference is in Kista, any hotel in Kista or on the blue line of the metro makes travelling to the conference faster and more convenient.
Please visit Vandrarhem Stockholm (Hostel Stockholm) to search more affordable accommodation options in the different parts of Stockholm city.