It looks like the TurboPack version on github is the best one at the moment.

As mentioned in https://en.delphipraxis.net/topic/6277-synedit-just-got-a-major-uplift/ in 2022 by @pyscriptor:

One of the major flaws of SynEdit was the poor handling of Unicode.  A major update has been committed to the TurboPack fork, that employs DirectWrite for text painting and fixes Unicode support. SynEdit should now be on a par with, if not better than, the best editors around with respect to Unicode handling.

And I see his big contribution there in the TurboPack fork.

Also we can compare activity:

• https://github.com/TurboPack/SynEdit/commits/master/ (last commit a month ago as of now)
• https://github.com/SynEdit/SynEdit/commits/master/ (last commit 3 years ago)