There's no "right" time to inoculate with MLB, though traditionally it has been done as you suggest, after AF is complete and the wine is under airlock. In my winemaking time over the last 7 or 8 years, I have been adding my MLB just after the start of AF, with great success, so I am a fan of that timing. Why? MLB effectiveness is governed primarily by four factors, nutrition, temperature, pH, and ABV %. If any one of these is out of the acceptable range for your particular MLB, it may cause issues, if any two are out of range, failure becomes more likely.
Understanding that we can control pH with additions, and nutrition with MLB nutrients, the other two factors are the only ones left in the equation. Inoculating early in AF allows your bacteria to become established in and environment that is virtually free of alcohol, and adapt to the increasing ABV slowly, and the temperatures created by AF are typically higher and conducive to good MLB health. Addtionally, red wine musts that still have pulp, and skins in the mix, increase the available nutrients for your MLB. These are the reasons I like to add the MLB early, and why I believe it to be so successful.
Dropping MLB directly into a wine with no skins or pulp, and with an ABV that is at or in excess to its ABV tolerance creates a stressful situation from the start, so if you wait until AF is completely finished, and your ABV is 14%, and your MLB strain has a tolerance of 14%, you're on the edge to begin with. My advice to you at this particular point in time is that you add your MLB sooner rather than later, and make sure your pH is in the good range, and you have enough nutrients on board, particularly since you're using a juice bucket, maintain temps in the mid 70's, and let your MLB get used to the ABV as it increases.
As for the WLP675, I've never used it and have seen lots of folks have issues getting it to start and complete MLF, so read about its requirements and do everything you can to give it a favorable environment to succeed.