White sugar is Sucrose (one molecule of glucose joined to one molecule of fructose), maltose is two molecules of glucose. Yeast cannot transfer disaccharides across the cell wall, so secrete an enzyme invertase (actually they don't it's part of the membrane transfer mechanism) which splits sucrose into glucose and fructose and maltose into glucose. These are then actively transported into the cell whereby the first step in the 'respiratory process' is to convert them to fructose 1,6 phosphate (IIRC this is from memory and I can't be bothered to look at my biochem book)
Cane or beet sugar is sucrose (99.6%) so in the fermenter works the same regardless of which is used. (although
there is evidence Cane Sugar is nasty stuff to make candi sugar from).
Brewing sugar is a generic term, and I would like to know the specification of it's make up (i.e. the listed ingredients), before making any wild claims . . . However, I
suspect that it is nothing more than dextrose which is a fancy name for glucose.
Now there are some claims that dextrose/glucose ferments cleaner than sucrose as the yeast don't have to switch on the invertase gene . . . and therefore don't produce invertase and it is invertase that is responsible for THT and the production of fusel alcohols. . . . if that was the case then all beer would suffer from it as wort consists of about 25% dextrins, 40% glucose and 35% maltose . . . which requires invertase in order for the yeast to utilise it.
Excessive use of sugar (Kit n kilo brewing), and the use of cheap kits (which already have a significant proportion of sugar in it anyway), produce a thin 'cidery' beer.
The use of 'old' kits and extract produce odd muddy flavours and a harsh bitterness which I attribute to THT . . . Fresh kits and fresh extract show no sign of THT.
Fusel Alcohols are typically produced when yeast is subjected to excessive high temperatures especially in the early stages of fermentation, and lead to a 'hot' alcohol taste, and generally a bad hangover in the morning which is not in proportion the the quantity drunk.