Buus didn't have many karting achievements from when he started in 2013, but his biggest achievement was coming second place in the 2015 Danish Championship - Cadet Junior class.[4][5] He also participated in various WSK events, including the WSK Super Master Series, WSK Final Cup and WSK Open Series. He finished 9th in the WSK Final Cup - OKJ class in 2017
Aquila Synergy Cup
In 2018, Buus made his debut in the Aquila Synergy Cup, where he achieved much for success then he did in karting.[4] He won 9 races and got 14 podiums out of the 15 races he was in, with 3 poles and 8 fastest laps, he came 2nd in the championship with 450 points.
GT4 European Series
Buus's first appearance in GT4's was competing in the 2020 GT4 European Series Pro-Am class full time for Allied-Racing alongside Jan Kasperlik.[5][6] The pair beat former Formula 2 driver and current Super Formula driver, Cem Bölükbaşı and Yağız Gedik to the Pro-Am title, winning 8 out of 12 races.[7][4]
Buus contested the final round of the 2021 GT4 European Series with Allied Racing, partnering Joel Sturm in the Silver class.[8] The pair won a race that lifted Buus to being classified as 17th in the championship standings with 25 points.[9][10]
DTM Trophy
Buus made an appearance for Allied Racing for the second to last round of the 2020 DTM Trophy in Zolder, replacing Felix Hirsiger. He scored 12 points in the two races he drove in.[11]
In 2021 he competed in the Porsche Carrera Cup Germany full time, as he fought for the rookie title and also fought for podiums in the overall standings, getting his maiden podium in race 1 of the second race in Monza, and another podium in the final race of the final round of the championship in Hockenheim.[3][12] He finished the championship in seventh with 120 points.[13] Buus was pipped to the rookie title by Loek Hartog, as the Dane was runner up to the rookie classification.[13][14]
For his 2022 campaign, he competed full time in the Porsche Carrera Cup Germany and in the 2022 Porsche Carrera Cup France for Allied Racing.[3][13] He achieved his maiden win in the Porsche Carrera Cup Germany in the first race of Imola, and got his maiden pole in the first race of Lausitzring.[15][16] He finished his campaign in fourth with 8 podiums and 236 points.
In the Porsche Carrera Cup France, he didn't win any races but got 6 podiums and won the rookie classification, finishing his maiden season with 137 points in fourth.