When we had to do this for hours of sourcefootage in multiple languages, we had timecoded translations and used an app that generated subtitles from the translations that were timed based on a word count from each timecode reference.
More timecodes in the translations increased accuracy of the subs
The app generated PNG files for us but could also export other formats to import as PPro or Avid subtitles.
Apps used: video toolsheds ‘make transcriber files’ (for BITC audio for transcription/translation and ‘Subbits’ for the subtitle generation.