Miles is BIGGGGG on pet names.
Of course, he calls Gwen "Mi amor". That's typically the one he pulls out when he's feeling supeerrrrrrrrr lovey. When all he wants is to pull her in and kiss her all over. His moods + the "Mi amor" always leave Gwen a blushing giggling mess.
Years down the road, "Mi amor" is also what he pulls out when he wants to embarrass his kids and drive them up the wall - literally. One time he was being so "gross" in his displays of affection (Charlotte's words), that she and Max literally climbed on the wall and started yelling at their parents to "stop being disgusting".
I think he'd mainly call Gwen "Baby". It's probably just the name that stuck the most. I could also see him being in the same boat as Jake Sully with the "Baby's". Like he calls Gwen "Baby" more than her name. When he's loving on her, when she's sad, when she's frustrated, when they're on the job, etc.
"Baby, what's wrong? Come on talk to me."
"BABY! BABY THE CAT - THE CAT'S DOING THE THING AGAIN" (I headcanon that they got Charlotte a cat for her 4th birthday. Miles was not a fan)
"Baby, can you take care of that guy? My hands are a bit full here."
"Baby, just calm down. Please do not do this right now, Baby. We can take care of it later."
Gwen on the other hand doesn't use pet names too much. I think she really just prefers to use Miles' name. And I mean, have y'all heard the way she says his name? It's filled with so much love already that honestly she doesn't need to use pet names.
However....I think she does call him "Babe" a lot
Their friends probably hate the word now because every time they're with Miles and Gwen it's just
"Babe can you grab Charlotte's pacifier?"
"Hey Babe! Didn't know you were joining us!"
"BABE." (followed by a glare and hands on her hips)
Sometimes it's used lovingly and in a positive light, sometimes (based on Gwen's tone) it means Miles is in trouble.