A system with a silencer between the hood and the blower, whether the blower is in-line or external, will be quieter, given equivalent blower qualities.

A 42-inch wide hood, of sufficient depth, will be better at capture of rising and expanding cooking plume effluent than a 36-inch hood.

Also depends on the length of the run.

Although I am not completely familiar with Broan hoods, I believe they are typically made with a 6" duct or maybe less. If you are worried about how quiet your hood is you need to make sure that your duct size going through your home is minimum 8", although 10" duct would be more sufficient. The reason for this is because with a 6" duct you can only produce a maximum of give or take 600CFM because there is too much air resistance for it to be able to support 1000CFM. So although your blower may be 1000CFM, you won't get true 1000CFM unless you have a minimum duct of 8" and in fact you'll just create more noise if you try to push that much CFM through a 6" duct. You also need to take into consideration of makeup air if you are using a blower this powerful, you may have already looked into this but you need to make sure that you have enough air coming into the kitchen for such a powerful blower or else you'll create negative are pressure.

The difference between in interior blower and inline blower is primarily noise and install complexity. all things being equal they should work roughly the same. The fit and finish on the thermador hood itself will be superior (fewer sharp edges, nicer quality controls etc) but otherwise similar in performance.

HLB11 is a 10" round so no need to worry there.