Timing is tough to recommend. If the plant is unfamiliar, it really makes a difference how long it grows after it enters flower as far as when to lollipop and not hurt your yield. You do it too late and you potentially cut off good buds, and if too early, you end up with more larf than you want.
Don't think it improves your yield. At best it helps eliminate larf and hopefully if done at the right time, some of that is redistributed flower growth.
On super-stretchers, lollipop to 2-3 nodes on each cola about 5-7 days into flower (if autoflower, around the time you see preflowers). If it's a regular 2x stretcher, lollipop around flip. With strong ligths and not over-crowding the canopy, should have 18-24" long stack of nice buds - not larf. Don't exceed 3-4 colas per sq ft and keep them level.
Even the 2-3 nodes part of that suggestion depends. I consider how much of a branch has formed and space to handle it in future. I don't want moreo than 2-4 larger side branches. I use a scrog to keep base of plants low, so once in position i usually take off the first branch or two above the scrog and everything below it.
leaves are small... did you defoliate? That tends to cause small leaves because all the mature growth gets cut off for no benefit whatsoever. Don't defoliate just to defoliate and you won't have tiny leaves.
Like others said, i don't think there's any point at this stage for this plant picturered. Maybe if something in the central lower area is incredibly shielded or will cause congestion, so if you do cut something off be very selective. once the buds sites are forming, it really won't redistribute anything, if that is even a thing, so it'd just be removing yield.