My thoughts on Mike
This may not be very original but I'm thinking about him and wanna write about him.
No, he's not just a more self righteous Walt. I think the main reason was his criminality was never a taboo to break (given his upbringing). It's implied Walt grew up fairly comfortable. While not much is said about his mother, I actually don't think she was a Livia Soprano, but was fairly loving and probably quite patronising, which Walt was embarrassed by (but that's it's own can of worms). Mike grew up poor on the streets of Philly with a failed deadbeat dad. Crime was normal to him. He likely fought in Vietnam voluntarily (it's implied he was a sniper) implying he was at some point patriotic and optimistic, and lost much of his optimism between this and taking his first bribe when he came back home and served as a Philly beat cop, seeing the worst of America day to day.
What Mike never lost (or possibly regained seeing his son’s moral steadfastness) was his value for human life. For Mike, whose life was a father he couldn't rely on, fighting a brutal war in Vietnam for nothing and then spending the next few decades of his life in a corrupt police force seeing the worst society has to offer (namely the wife beater he describes to Walt). To Mike, crime was the norm. To Walt it was the exception. Mike, a corrupt man who was never truly at peace with what he was doing, was set apart by his empathy. Walt, a straight arrow genius who was looked down on most of his adult life by people less smart than him was set apart by his pride and ego (and he eventually had an excuse to let his demons loose once he was told he'd be dead in two years).
Where they are similar, however, is A: they both enjoyed much of what they did (who doesn't like succeeding in their field?) and more importantly, their lack of value for morals. Mike dodges moral responsibility and tries to atone for it by taking the full brunt of emotional responsibility. We see this with Werner, a man Mike values, and the first time since he avenges his son that he breaks his new rule of never killing. Better Call Saul is largely the story of two guys trying to change and failing, and Mike killing Werner was the beeping red light, but what I find interesting was Mike choosing to kill Werner himself. Of course, a part of this was empathy and sparing him from being tortured by Gus’ men, but I also think Mike does this to atone for his role (as a criminal conspirator) in getting Werner killed so he can continue never having to do the right thing. By looking Werner in the eyes, telling him what has to happen and pulling the trigger on him he gets to play the “I’m a bad man, I know what I'm getting into and I'll accept the consequences” card, which is his main way of getting out of responsibility. Same with Nacho, who he beats up instead of letting Gus’ men do it, and looks in the eye and talks to before he's handed over to the Cartel.
The speeches Mike gives to Jimmy expose him a bit I think. His “I do this for my family and understand it's my fault if I get caught or killed” speech in the desert would be the prime example. I think this and Gus’ “a man provides” speech resonates with people, not just because it tells you to do more for your loved ones, but also the idea of having a free pass to be ruthless and immoral to do so is something people resonate with. Being good and moral is difficult, and people want to ease the burden by reducing the scope of their morality. Mike very much meets his match when he confronts Nacho’s father, ready to atone for Nacho’s death by telling a father his son is dead. He tells the father he'll seek justice, but the father shoots him in the eye with complete indifference as to which criminals face justice and which don't, which cuts deeply at mike who deep down sees himself as one of the good ones.