And the usual answer is - it depends. On how much work you’re doing on lifting days. And on how you work the conditioning/GPP in. Slow buildup of work capacity is best. 1 or sets or rounds of something and build it up week by week incrementally.
I have no patience and always do too much on recovery days when I try to add stuff. I can see the sense of it, but can’t take my own advice. I always end up paying for it by damaging my lifts with fatigue.
My current routine is flexible in that certain lifts are not tied to any particular day of the week. I just do a back and forth between two routines right now with a day between them. If I get overdone, I’ll just take an extra rest day or do a deload cycle or two if needed.
On my previous program, which I see myself gravitating back to, there was no way I was going to do anything on non-lifting days. The previous day’s volume demanded complete rest.
Light barbell complexes
Sled pulling (when I had access to one those two whole weeks…)
Goosing female joggers and running like hell