Again, the keepers aren't that smart. They're a choke chain meant to correct wrong behaviour. They *cannot* take total control of a person's mind, nor dictate their every word and they're only as cunning or attentive as the Drakh at the other end of the link.
The Drakh don't care one whit if Londo tells a story about the Minbari War to a pair of children. Just like they don't care if he scratches his arse or exiles his wife (long story.) If it doesn't directly effect their agenda, then it's not relevant.
As for why the Drakh don't put keepers on Vir, Delenn, Sheridan etc: The Drakh are not omnipresent. Hell, I don't think they're even that numerous. They can't just stroll into Tuzanor without the Minbari A) noticing and B) killing them. As for Vir...you'll have to read the books. Deal with it!
So, Kirk...does *this* sound like a puppet? (Potential spoilers of a movie you're determined not to see because of your own overthinking)
"The Humans I think knew they were doomed, but where another race would surrender to despair, the Humans fought back with even greater strength. They made the Minbari fight for every inch of space. They would weep, they would pray, they would say goodbye to their loved ones, and then throw themselves without fear or hesitation at the very face of death itself, never surrendering. No one who saw them fighting against the inevitable could help but be moved to tears by their courage, their stubborn nobility. When they ran out ships, they used guns. When they ran out of guns they used knives, and sticks, and bare hands....They were.........magnificent. I only hope that when it is my time, I may die with half as much dignity as I saw in their eyes in the end. They did this for two years. They never ran out of courage, but in the end, they ran out of time."
Emperor Londo Mollari. "In the Beginning"
As for your question about Vir and keepers/Drakh...read the books. Don't expect us to tell you so that you can come up with some other uninformed opinion.
Let's see if he can be arsed to watch a 3 minute clip.
It's worth keeping in mind that these are the words of a man who knows full well that he *will* die within the next few hours, with his best friend's hands around his throat.
I'm actually a little temped to quote something else Londo says to a certain human General in this film about "efficiency"...but maybe that'd be pushing things just a little too far.