Hello,
The main difference between the Better and Advanced grades lies in the selection of the wood itself and the overall craftsmanship.
As for customization, you are mostly right — Better bows are generally not customizable. In most cases that is true, but occasionally there may be a bow already in stock that happens to match the detailed specifications you need at our quantity. It can help if we talk about some details about it.
Regarding the length of the our stock Better baroque violin bow, it is 68 cm without the button(screw), the total length can be about 70 or 72-73cm
Hope this helps!