Hey D
I've been running a Herbie for 5-1/2 years and find it very quiet on a 75g running an Eheim 1262.
My first tank leaked after about 4 years. I bought an Elite Aquatics 3-drain unit for the replacement tank, but decided to plug 1 and still run a Herbie. I've heard about Bean Animal setups sometimes being noisy and never had any issues with the Herbie. Couple times a month it needs a valve tweak, but no big deal.
If you're going straight down to the sump, 1" will be enough for your main/full siphon. I run 1-1/2" about 8' with multiple 90s and find it's almost too much.
For your emerg 1-1/2" would be better than 2" if it ever needs to go into full siphon mode. 2" is fine if you're already set up for it. And it will be noisy as hell -
sucking/gurgling - so you'll know if it's running.
My first build was an Aqueon. I was stuck with running a 3/4" main and 1" emerg - over horizontal runs too - it never failed.
I would recommend you don't run your overflow box to a 'fuge. It'll need it's own valve and will mess up the main drain balance. Water will take the easiest route and you'll be playing with valves constantly fighting air/water between the 2.
Even a fluctuating level in your return section will mess up your tuning. Not having an ATO will drive you batty.
It'll take you some time to find the balance of the main drain, and it's all you want to deal with from your overflow box.
Instead, think about running the fuge from a stable section in your sump. If you run it from the box, you will lose the stability of the overflow.
And if you run it from the return pump section, you'll get DT and 'fuge fluctuations.
I tried it years ago running a 'fuge above my sump - plumbed from the return section with a separate pump and draining back to it - it drove me nuts trying to keep the fuge stable, and it messed with the DT level, so I gave up.
If you want a separate 'fuge, think about running it from and back to the section before your return pump. I feel that once this is dialed in it should remain stable enough, but you'll find out.
Best advice I can give you about it is, if you want a 'fuge, design it so you can try it plumbed 'from and to' different parts of your sump. This way you can play around until you find what works for you.
I built my first one into the sump and had to cut it out. The second one was on a shelf over the sump. That was a fail too.
As I said, I gave up
I now rely on deep crevices in my LR to allow pods/mysids/stars to thrive and it's enough for my needs. If you're looking for pod growth, consider rock piles your fish can't get into.