I always think of it like this:
BL and GL are generally when the genre of the story is Romance, but it's a m/m or f/f relationship. Readers will generally expect the story itself to be equivalent to the Romance genre, with the relationship being the core driving part of the narrative and the central conflict and stakes all revolving around "how do they get together?" and "what threatens their relationship", it will be assumed that by the end of the story, the characters will be together.
LGBTQ on the other hand, I'd assume the story involves one or more LGBTQIA characters, and it might even have a relationship or two, but the core story isn't about that romance.
So let's imagine there are two comics about a superhero guy who falls in love with a supervillain guy.
In comic number 1, through a series of funny and dramatic encounters they fall for each other and eventually the villain is redeemed by the power of love leading to a dramatic climax where the villain's jealous henchwoman tries to break them apart, but fails. There's a happy ending. This one is a textbook BL with Action elements.
In comic number 2, the hero and villain keep meeting and having these encounters and even have sex, but then realise they don't really love each other, they're just obsessed, sexually frustrated and lonely. The villain redeems himself, realising that his internalised homophobia and isolation were the cause of his hatred of society, and there's a happy ending where they both go out into the world as better people and get into fulfilling relationships with lovely guys... but they're not with each other. This one is more LGBTQ/Action, because queer identity and relationships are very important to the plot, but it's not a Romance and the stakes were "can this villain be redeemed before he destroys the city" not "can their love bloom before they're driven apart?".