OT also has 8 tracks of MIDI sequencing which are pretty fun. Meeblip might be a good way to go to get your feet wet, https://meeblip.com/
Would definitely recommend going with a synth with DIN midi though, given the OT’s DIN only (no midi over USB). I had an OT and OP-1, I liked passing OP-1 audio through the OT, but regretted not having a synth that I could hook up directly to MIDI.