We need to realize that gandhabba can have many varieties: human (good and bad), animal (bad) are major types. By “bad”, I mean they have “bad gati” and are likely to “smell bad” if they have dense enough bodies.
In addition, there are some peta gandhabbas (bad) and deva gandhabbas belonging to the lowest deva realm (good).
Gandhabbas can inhale and have fairly dense (still mostly unseen by normal humans). Bad gandhabbas inhale “bad odors” of waste and even feces. Good gandhabbas inhale scents of flowers, leaves etc.
As is the general rule, good gandhabbas are attracted to good environments and bad ones to bad and dirty environments. This makes some dirty environments even more “smelly”. That is one reason why we need to keep our living environments clean.
So, when one is in the gandhabba state, one can feel really good (like in the case of Vilas). They don’t have the burdens associated with a heavy physical body AND their minds are not burdened with defilements.
On the other hand, “bad” human gandhabbas (which is the case for even some human gandhabbas) have “smelly bodies” and their minds are defiled too.
Gandhabba has a bad connotation due to misconceptions. A Brahma‘s body is essentially the body of a gandhabba (without even a trace of the karaja kaya or the physical body). One who cultivates jhana and can come out of the physical body (like Vilas), essentially has a “Brhama body”.
– When such a person dies, he/she is born in a Brahma realm (unless of course attain Nibbana before death). Even in the case where one has cultivated anariya jhana, the next birth is in a Brahma realm (corresponding to the particular jhana cultivated).
– But of course, those with anariya jhana come back to the human realm and can be born in the apayas in the future.
P.S. Those who get to the Anagami stage (i.e., remove kama raga and patigha anusaya) also are born in Brahma realms even if they have not cultivated jhana.