I am not sure anymore what is regarded as an overstepped boundary in the world we live in
OK. Firstly, there are no 'universal' boundaries. They are all personal and everyone's will be slightly different.
You don't need to tolerate anything just because you think someone else might!
Secondly, I'm going to share with you what my relationship looks like in this respect. Some would think it fine. Others would not. But since you asked more in general terms, it might help to read it.
My partner is a very tactile person and a big hugger. I wouldn't describe him as flirty but he does have a couple of very longstanding, comfortable friendships with the wives of even longer standing friends and, whilst he doesn't 'flirt' with them, he is sometimes a bit 'flritarious' around them sometimes, but it's all done in jest and not at all 'inappropriate'. If that makes sense? It's just part of their friendship and not at all 'intimate'. There's no meaning or intent behind any of it and it never makes anyone feel uncomfortable.
He always greets his close friends (male and female and mine too!) with a big hug and a kiss on the cheek, all of his friends do. Before we got together, there were a couple of the female friends that he would give a peck on the lips to. Again, it wasn't 'intimate' but he's not done it since we got together. Not because I said anything but because thats clearly his boundary.
But it was still not inappropriate. Their husbands and he were also great friends. It's just how they were/are. I know he messages at least one of his female friends frequently because I see her name on his WA. But I have absolutely zero concerns. He's said they talk about films and books. I wouldn't know - I've never looked and feel no need to.
I can imagine that this friend might sit on his knees in a, "There's nowhere to sit so I'm perching here," kind of way. But there is absolutely no way that he would allow another woman to sit on his lap properly, stroke her hair or talk to her face whilst he's holding her. That's just far too intimate.
I'm not a 'cool wife' in any sense! But none of those interactions have ever felt disrespectful. The dynamics between him and them, and them and me are totally different to you describe. I have no problems with affection being expressed physically. He's far more tactile than I am though!
For additional context, there was a woman, actually a mutual friend of both of ours who did start to behave inappropriately around him. Because his boundaries are slightly different to mine, he didn't initially realise that he was just being himself but the dynamics, and intent on her part, were different and that she was being more 'intimate' towards him in her behaviours. But he also did put boundaries in place after we'd spoken about it because he loves me. She didn't react well to that, he saw it clearly after that, and now we no longer see her.
You are not comfortable and whether anyone else would be happy or not, is irrelevant.