I can't really say I'm a "comp" player nor currently play Bannerlord MP, but I love M&B combat and am pretty into martial arts, and train in boxing on an almost daily basis and have done so for a fair bit. I find that there are some similarities in the overall dynamic of the two artforms, boxing and M&B. I've done a little of Longsword fencing but most of my knowledge, and especially experience and skill, are in boxing, (I'm not anything impressive though) and fencing and Boxing both have very, very similar dynamics and principles, both essentially being striking arts.
M&B is certainly not "proper" compared to something like HEMA artforms, but for a videogame, it hits pretty close, particularly with the speed, little mistakes potentially costing dearly and able to be exploited, and the massive importance of range and footwork and the subtle aspects to those. Stuff like Chivalry and Mordhau is too slow and exaggerated to feel very real. M&B feels much faster in my opinion. Speed and accuracy is what matters in any striking art, less so meaty power. In addition, the absolute ridiculous skill ceiling and learning curve of M&B combat feels similar to any irl martial art, you could train for 30 years in one thing, be it Wrestling, Boxing, Judo, BJJ, Kickboxing, Muay Thai, whatever, and still have massive room for improvement.
On the surface level M&B is pretty simple, you have four attack directions, four blocks, and a weird, step-less front kick. Boxing also looks simple on its surface level, you have four main types of strikes, (jab, cross, hooks, uppercuts) can block them, parry them, slip them, simply pull back or step away from, or weave under them. But both go unbelievably deep compared to what this apparent simplicity would deceive. It's like an onion, you'll peel one layer, thinking you start having it down, only to discover so many more levels.
So mainly, in my opinion at least, M&B combat is realistic with the overall dynamic and principles, not so much the actual movements. Higher-level Warband dueling may look janky, for instance, but damn if it doesn't feel good and realistic to be in. Some of the footwork that you would do in M&B is pretty similar to what you would/could do in Boxing. That's mainly why I've loved M&B combat so much, it's realism, massive fun, and towering skill-ceiling. Too bad both Warband and Bannerlord are kinda dead, one because of age, the other due to TW's incompetence with the MP.