the differences are
TX = No sunroof / No wodeen Panels / Interior fabric is less quality / no Dual AC (only real disadvantage only when you nedd to haul all seven passengers , otherwise front ac is enough or 5 passengers. And who needs to operate sunroof. i have never used it in my TZ)
TX limited = sunroof/ good quality fabric (lik tz) / wood panels (like tz) / no Dual Ac
TZ = All of above things included , ncluding Dual AC (really helpfull in cross country travelling)
TZ G grade = all of above + power seats + leather interior
As for fuel consumtion all 1kz engines hve 6~7 in city and 9~10 on highway (tested many times when travelling from karachi to northern areas.