at 8 months, the texture you are looking at should be a thick, smooth "base" with some lumpy bits in.
the lumpy bits should be very soft, which can easily melt in the mouth, size is bigger than cooked rice. when
when you think he can handle the lumpy bits well, you can make the size bigger and bigger ... so on.
i think for finger food, cheerio and biscuits are fine, as it will melt in the mouth and it's dry and won't slip into the throat easily.
eating is the same with other development, every baby is different, so take your time and enjoy every step !
HTH