In general I was pleased with how little VAR interfered with the flow of the game. The biggest thing for me to get used to is the referee not blowing for offside until the phase of play is complete - the players have obviously been drilled to play to the whistle, but my brain is clearly less malleable and still has dissonance seeing play continue while the lino's flag is up.
Would your opinion on tight offsides change based on what the original call was? If the lino flagged that as offside, and the VAR agreed, I think most people would say "wow, what an amazing call!". But as it's a machine over-ruling a human, people seem to be more anti-VAR about it.
If you want the original ruling to stand when it's so close, what is your limit for "close"? An inch? Then you have to worry about whether VAR says you're 0.9" or 1.1" offside, and the problem hasn't really been solved. May as well just simplify to "computer says no".
But then there's the technical aspect of whether you can determine exactly when the ball was played accurately enough. Do you know what frame rate the VAR cameras run at?
Yeah it's a good point about where the decision line falls that I don't have a good answer for; it will always have to be somewhere and there will always be uncertainty. I guess I'm just not sure I agree with the premise that offside is always an objective call, and it seems like the "clear and obvious error" criteria should be applicable (and in this case wasn't met).
Having said that, it is as you say also really dependent on the technology (I don't know what the frame rate is). It's possible they have better angles and cameras than the broadcast has, in which case maybe there's clearer evidence for this being offside and we just don't get to see it. But if not and it's a question of an inch or whatever, it seems like there's too much uncertainty regarding exactly when the ball is hit, exactly what position the player was in at the time, and even exactly where the arms stop and the shoulders begin.
As far as the AR's call in the moment, I'd actually definitely not want them to flag this, for the simple reason that it's next to impossible for the human eye to see something that close accurately in real time one way or the other. The AR is basically guessing there and is as likely as not to be wrong, in which case he should always err on the side of letting play continue. Especially so in a competition with VAR where continuation can always be overturned, but a stoppage obviously can't be reversed.
Side note: in a lower-level/normal game without VAR it can also be context-dependent, i.e. if the score is 4-0, maybe on a tight call that could go either way you hedge toward the team that's losing. If it's a match-critical decision in the 88th minute of a tied game, you give it to the team that's been less annoying all game long ;)