Converting MTS to MP4 to add keywords

[PunyEarthling]

Hello! Making a 2-hour Premiere Pro multi-format movie for YouTube, not for Blu-ray disk. Experimenting with converting MTS files to MP4, lossless for editing, so keywords can be added to the clips in Adobe Bridge. 60% of the movie is MTS. MTS does not support keywords 😥. Conversion is a very long process timewise 🤪. Are there better ideas or am i stuck with weeks of conversions?

If unavoidable, converting from MTS AVC/H.264 (MPEG-4 Part 10) 1920x1080p60 to MP4 (MPEG-4 Part 14) 1080p60 H.264 High Quality lossless a/v, without compression, from Part 10 to Part 14. Many of the files will be reused in 6 future movies, so keywords are imperative. The finished movie will be exported to YouTube as close to that quality as possible for big screen tv viewing. Are my conversion settings correct, or should they be set at something else? Thanks!