Both Real Madrid and Manchester City, they both still have problems that greatly affect their game, so I think this is still a 50/50 chance for both teams that will compete. Although I see Real Madrid slightly more favored, but still it is not a guarantee that they will be able to win easily, just like you said. Maybe in the end luck will be the deciding factor for both teams, which will determine who can win this match.
With the conditions of the two teams that are not much different of course they have the same chance to lose, draw or win in the match, so I think besides luck of course the coach strategy will be the most important factor in supporting one of the teams to win in the match later, but I personally tend to see if the two teams might end the match in the first leg with a draw, regardless of who might be the winner in the second leg and qualify for the last 16, somehow I'm pretty sure that one of Madrid or Manchester City will be a serious contender for the championship if they make it to the knockout phase later, because I see the bad conditions they have experienced so far often do not affect their mentality when they are crucial matches in champions league .
The first leg match will be played at Manchester City's headquarters, it is a very crucial time for the host, because when playing as a host for me the only choice is to win. As for Real Madrid at least they must be able to hold Manchester City to a draw even though a bigger win would be very beneficial for them. But to get it is certainly very difficult. For the strategy that will be played by both coaches, I think the usual strategy will continue to be done. Manchester City with a strategy of dominating the game while Real Madrid with a pragmatic strategy and relying on fast counterattacks. Whoever makes the most mistakes will be the one to lose.