Hoo boy, it's a toughie. On the one hand, Trump would still be around. He also wouldn't be in as much legal peril as he is now (it's likely there wouldn't have been an appetite to prosecute him over the Stormy Daniels hush money payments, and the classified documents case would have never happened to begin with since he wouldn't have had access). But he almost definitely WOULD have tried to pull off another insurrection similar to Jan 6th--he was foreshadowing that he wouldn't accept the results if he lost even back in 2016, using the same language as he did in 2020 before he launched his coup attempt.

The world where Trump doesn't attempt a coup isn't very interesting, at least for this thought experiment--he slinks off, continues shitposting about Hillary on Twitter, but likely doesn't try to run again (or loses in the primary because he's a sore loser). Everyone ignores his hush money payments in the interest of "statesmanship," and at best he becomes a minor kingmaker in the party apparatus. MAGA withers on the vine, and we largely continue with the late Obama administration status quo.

The world where he attempts a coup is much more interesting. The real question is, what would have changed after the failed insurrection attempt? It's highly unlikely it would have succeeded or even gotten anywhere as close as it did, since a lot of the original plan relied on access to the levers of power (I.e. being able to withhold security to let the rioters overrun the Capitol). But how would everyone react to it long-term? In this timeline, Republicans genuinely distanced themselves from Trump and Jan 6th at first, likely out of shock over the realization that they were actually in danger and the very real fear that they could end up hurt or killed. But as the shock wore off, Republicans started shuffling back to MAGA as the propaganda machine did its work to downplay and normalize the failed coup, and they realized that their base saw Jan 6th as a good thing.

In a theoretical timeline where Trump tries a coup in 2016, it depends on how far Trump gets before he fails. If he's thwarted to the point where he doesn't (or can't) hold the rally that stormed the Capitol, then nothing really comes of it at all--it becomes a footnote in history that is only cared about by political historians, pub trivia enthusiasts, and people who like to talk about politics on the internet. If he gets to the point where he holds a rally, but the rally is prevented from interfering with the certification process (complete with provocative images of cops in riot gear swinging at MAGA rioters), it's likely that this downplaying and normalization would have been ironically amplified by virtue of the coup attempt being less successful. Without the visceral fear of hiding from rioters, Republicans would have no reason to distance themselves from the attempt, and they would almost immediately start using it as fodder to attack the new Clinton administration. In short, the hypothetical coup attempt would become another Benghazi scandal for Clinton--something that she had little real involvement in and largely wasn't her fault, but that she gets blamed for anyway. Trump, meanwhile, would remain largely in the same position as in 2015--the dominant force in the party.

Aside from that, the court wouldn't be as openly corrupt as it is now. It'd be filled by a moderate Clinton appointee if democrats have the 51 votes to abolish the filibuster for supreme court appointees (or held open by McConnell otherwise), and when RBG dies her replacement is decided by whoever wins the 2020 election. Roe v. Wade would still exist, the chevron deference would still be the law of the land, and we wouldn't have the terrifying prospect of legally sanctioned presidential death squads.

Overall, I think we would be largely in line with the status quo of 2014-2015. Not great, with a worrying trend towards fascism and an establishment largely too busy huffing their own farts to address the vast majority of problems facing us, but a LOT better than where we are right now.