Hi there, just another pretty obvious question here. Just need confirmation.

According to the augmentation p. 41

The move-by-wire system confers a bonus of +2 to
the character’s Reaction attribute, +1 to the character’s
Dodge skill rating, and +1 Initiative Pass per point of rating.

so it translates to +2 reaction for rating 1, +4 for rating 2, and +6 for rating 3

and since the highest augmented max is 9 or lower, does that mean if you plan to get MbW3 it would be pointless to increase your reaction past 3 via other ways like karma(natural)? so if i also put in a suprathyroid gland I only need to get reaction to a natural 2?

Thats right, unless you raise your natural max of reaction.
It's possible to get that up to 9, so then your augmented max would be 13 so at that point you need a natural reaction of 6 to reach the max with those two pieces of augmentation.

Yes, that's right, unless you somehow increase your augmented maximum.
Please note that MBWs are also compatible with Reaction Enhancers as well.
So if you have a lvl 3 MBW, Reaction Enhancers 3 and a Suprathyroid Gland and Genetic Optimization (REA) along with Increased Attribute and Metagenetic Improvement, you could have a Reaction attribute of 3(13).

And yes, unless you're a cyberzombie (who could get even higher than that), this means that a high natural Reaction is more or less redundant.
No other attribute is that easy to pump up with ware.

did not know about genetic optimization and metagenic improvement. i can probably find genetic optimization but where can i read metagenic improvement?

Genetic Optimization is in the geneware chapter of Augmentation.
Metagenetic Improvement is a positive Quality from Runer's Companion (in the Metagenetic Qualities section describing Qualities for SURGElings).

got it thanks

The handy thing about metagenic is that it raises your base attribute along with your max...so you have to spend even less on the actual reaction stat

The metagenic improvement and genetic optimization, along with exceptional attribute, allow for some crazy stats. I build a guy with 10 (15) Agility. His default (yea right, like he wouldn't have the skill) to fire a pistol would be 14 dice.