Don't even go there, Arsenal is still not that strong a club to contend with some external league champions when they meet at the UCL, it's always like that until they break the jinx. Real Madrid has always been a better side, fine, Arsenal is a good team now, they are trying their best even though they drew Brighton in their last match.
I was surprised about that match though, a club that could beat Aston Villa and Wolves 2-0 each found it difficult to win Brighton effortlessly. I know Brighton is not the weak team but Arsenal should still show them the supremacy if they are indeed to be watched out for as they seem this season. It got worse to the point that Brighton played them like a lesser team and I wonder why Arsenal was reduced that way, the feat was never there, perhaps they underrated the club but certain, if any EPL club is serious Brighton is certainly not the team you suppose to undermine, and with what they played last week I am beginning to suspect that it's the club we should also watch out for this season.

Nobody knows Arsenal's true strength this season but what is clear in the last 2 seasons Arsenal's performance has always improved for the better so I think we also can't underestimate Arsenal this season to be able to compete in the Champion League stage.
The draw against Brighton last weekend I think doesn't need to be considered too much because Arsenal was a little unlucky during that match when one of their players got a red card at the end of the first half which made it difficult for them to develop their game in the second half so that the final result of this match was a draw.
In my opinion Arsenal will still be favored in the competition for the PL title this season and they are also considered in the Champion League, if I'm not mistaken the bookies put Arsenal as the 4th favorite to win the UCL this season which means Arsenal's strength is very much taken into account now.