Note that I am far less experienced and weaker than you, so my suggestions might be either complete nonsense for you, but maybe they do make sense at least in spirit.
What I like for recovery work (and often, assistance in general) is doing 5 sets of 10 reps, with the same weight for all sets. Chose the weight such that it gets challenging in the last set, but still away from failure. Then perform each repetition with a big focus on feeling the muscle work (what bodybuilders call mind muscle connection). Rest times are kept short, sometimes I only rest for a couple of seconds, sometimes it gets a bit longer. Just until I feel ready again.
Increase the weight only once you really are bored with that weight and you feel like you really squeezed every bit out of it, usually after a few weeks.
Chosing such a high set number ensures that the weight is (at least for me) low enough to not take away from the other lifts.
What I find very important in recovery work that it is not only light on the muscle, but also light on the mind. For example, I hate doing good mornings with more than 5 reps, so if I were to do them for recovery, I would perhaps do 5 sets of 5 reps, but again with a weight chosen so lightly, that I can easily do all sets and concentrate fully on the muscles used. On the other hand, sometimes even 10 reps feels very heavy and then I do several sets of 20 on certain exercises.
Sometimes I also like to do just one set with 20+ reps.
As for exercise selection, for lower body I came to like doing lunges, just with bodyweight, and only measuring distance, so I do not have to count and use it also sort of a stretching and mobilizing exercise, going more by feel than any particular technique. Leg Curls and some Calve machine are also favorites of mine.
For upper body I would throw Lat Pulldowns with various grips in the mix. Pulling more vertically might also help destress by decompressing the spine, although that might as well be an old wive's tale.
Using such light loads usually allows me also to do row variants which would tax the lower back otherwise, so maybe even horizontal barbell rows (maybe standing on a box, if the bar would touch the floor in the lowest position) are possible again, but again, I pull about 150kg less, so maybe any row you do is already more taxing on the lower back than my best pull. :-D