Hey Mark,

Welcome!

I would definitely go the custom build route. As was said, you get exactly what you want/need.

If money ain't a problem, that's good. Very good. Not that you need to spend big bucks (thousands) for a 1st, good grow, but... it can go to your head (trust me, I know about buying un-necessary stuff).

<><><>
Smell: I haven't used ionizers, ozone generators, etc... so I can't comment reliably. But carbon filters will work perfectly... no smell.

As for stealth, understand that you will have various cables (probably) running into your box. I don't know your garage, but maybe you can carefully place the cables throught the floor/wall edge, and nobody notices.

Question: Is the stealth part, more like:
-You don't want it to look blatantly like a grow setup. So people can walk into the garage with you, grab whatever, then leave without noticing...

Or is it stealth like:
-absolutely 100% stealth...

????

Both of them are doable... just that the "100% stealth" thing is very difficult (fan noises (there are mufflers), the cables, a big box in the garage, etc.)
....

Nothing, just two or three things to shoot for.

I converted your measurements, for the other half of us ( )
80 centimeter = 2.624 ft
56 centimeter = 1.837 ft
100 centimeter = 3.280 ft

Will you be using HIDs? (High Intensity Discharge bulbs... ie, HPS, MH (high peressure sodium, metal halide)? They'll give the best results.