Hi,
1. Well, aside from completely removing these menu items for everyone I don't see any solution.
You can do that in your PHPMyAdmin in the menus table of Joomla.
However, note that you'll get the menu items back each time your update HikaShop, so I can't even recommand that.
2. The brands manager actually uses the exact same views as the categories manager. In fact, from one, you can access the others.
So that's why there is no specific ACL setting for brands. If you change the category ACL, it will affect both the brands and the categories.
What you could do is add such code:
if(@$child['check']['filter_id'] == 'manufacturer') continue;
after the line:
foreach($menu['children'] as $child) {
in the file "default" of the view "menu" via the menu Display>Views.
That will remove the brands menu.