I've had the best results with a little prelean at brace. I'll generally set the idler so an arrow laying on the left side (right hand bow) of the idler wheel has the tip of the arrow just on the opposite edge of the string at the nock point. Usually a minor yoke adjustment is all that's needed for perfect bare shaft flight.
I've started with no lean before but the prelean above is where it always ends up in the end without getting centershot jacked.

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Bow is at brace.
If a right handed bow,
pinch an arrow to the LEFT side of the idler wheel.

ALL bows, binary cam bow, single cam bow, twin cam bow (has two yoke cables top and bottom), ALL bows need pre-lean at brace height. WHY? Cuz you have a roller guard, or cable guard, to pull the cables sideways RIGHT at full draw, to get vane clearance. So what?

Cables get TIGHT at full draw only. So, cuz the cables pull the cam and the idler wheel to the RIGHT, cuz the cable guard is on the RIGHT, the top axle will rotate clockwise, at full draw.

Again. SO WHAT?

Cuz, the idler wheel ALWAYS rotates RIGHT (Clockwise) at full draw,
you have to have the idler wheel PRE-LEANING a little LEFT (counter-clockwise) at brace.

So, when you have the arrow PINCHED to the left side of the idler wheel,
SLIDE the arrow up or down, until the POINT of the arrow is at the same height as the middle of the d-loop.

YOU WANT the point of the arrow ruler to look like this.



Adjust the twists on BOTH yoke legs, for the top axle,
to rotate the axle enough, so the tip of your ruler arrow looks like THIS.



THIS means you have just enough PRE-LEAN angle, for the top cam.

BUT, what if I get a MASSIVE Left TEAR? DO I put more and more and even MORE twists in the the left yoke leg?
No.

THEN, How Do I fix my MASSIVE left tear?
Drop the draw length.



If you look like this,
arrow is pointing due NORTH (12-o'clock in the picture)
and your elbow is pointing at 7-o'clock, half way to 8-o'clock...NO amount of yoke tuning will fix this massive left tear.

DROP the draw length shorter and shorter, until you look like this at full draw.





When your elbow is at 6-o'clock, and your arrow is pointing due north at 12-o'clock,
NOW the left tear will go away.

So, what's YOKE tuning for? To make minor adjustments,
to tighten up groups that are 2-inches wide, down to 1.75 inches wide....where you have a bullet hole and still get
2-inch wide groups, and where you still have the same bullet hole, but you SKINNY up your groups, down to
1.75-inches wides.

 

Best is zero cam lean at brace; zero cam lean at full draw; zero horizontal nock travel during the draw. But whether its achievable is dependent on the limb deflections on the bow. Cam lean is a byproduct (often unfortunate byproduct) of the limb deflections; not something you adjust like your sights. The tuning process will determine how the cam leans (if it does). When a bow "likes a little pre-lean at brace"; its because the limbs on side or the other are too stiff (not matched well). Its really not possible for a manufacturer to engineering a perfect setup because every archer will hold the bow different, anchor different, etc. You might tune your bow and have the top cam leaning slightly like this (/) and then i shoot and retune it for me and have it leaning like this (\).