On a side note, as you are 1000 rated player, i advice you to focus less on reclaim issue like this, and learn managing your eco in a better way. Like not power stalling (seeing the power stall coming), not wasting mass (seeing the sudden mass incoming), having a better map awareness, predicting your opponent with better scouting, managing your army in a better way (knowing when to split your army to inflict more damage with raid, or to avoid/take the fight), and having some more longer term plan (going T2 land pretty fast, trying some droping tryhard play, skipping T2 land, multi-tasking and setting your opponent on fire with T2 gunships.....)
This will help your improve more easily, when you will learn this, you will then thing about the perfect number of pgen depending of the reclaim nearby your starting points, and how to effectively spend your time between reclaiming (manual reclaim) and the rest.

There are some things I tried but failed fairly often. Take Williamson's for example. It is a map where every unit early on counts, so I tried to improve my early build. To save a pgen, I tried manual reclaim of tree groups. The problem is threefold:

There are some trees which do not come in groups. You simply have to memorise this. There is no visual indication as to when this is the case.

If you want to reclaim those groups efficiently, you need to do it manually. This opens up a new set of problems.
There is no indication how big the tree group is and where it's centre is. Sometimes a move command will break the group because a tree standing a mile away belongs to it, making the engie waste valuable travel time on just a single tree.

Queuing up the move and reclaim orders, switching hotkeys every time is not something I really enjoy. If you use the button for reclaim or move, you give the command by left clicking while I am used to reclaim bigger rocks by right clicking. So after managing to change from move to reclaim fast enough and give a couple of commands (not messing up already), I then manage to screw up not knowing if my reclaim is still active. This is especially problematic if the mouse is still hovering over the last tree group, showing the reclaim icon either way. But if you now left click to deselect the unit, you give a reclaim command deleting the queue.

Attackmove behaviour is sometimes erratic. Sometimes the engie just won't pick stuff up. On other times, when I make a mistake because I didn't prepare for mass and overflow, all those commands are lost and the engie will start mowing down trees. Usually it's "go there and reclaim on the way" but sometimes it's "go there and reclaim after you arrive".

Why can't I just reclaim the tree groups by just right clicking them? It's not like I didn't understand why I have to, it's not like I wouldn't have to pay time and focus doing it. To me it just seems needlessly complicated and frustrating the way it is.