Romelu Lukaku put the Red Devils in front shortly after the break but Choupo-Moting levelled in the 63rd minute, heading in Xherdan Shaqiri's corner at the back post.
The wing-back's robust challenge on Hector Bellerin that allowed him to score is likely to draw post-match rancour from Arsene Wenger, but the suspended Gunners manager could have no complaints when those alongside him in the stand were brought
Steven Berghuis reminded Brighton not to let their guard down as he struck the post for Ajax, but that was one of few chances for the visitors as the Seagulls closed out a comfortable win.
Spurs failed to have a shot on target in the first half but improved in the second period, with Richarlison twice seeing efforts ruled out for offside.
Luis Enrique's side dominated and thought they had doubled their lead in the 48th minute, but Ousmane Dembele's fine curling finish was ruled out by the video assistant referee for a foul in the build up.
Natalya sent Naomi into the post, then rolled her back in the ring and locked in the Sharpshooter, forcing Naomi to tap out. - Dolph Ziggler came out and once again insulted the fans for only liking gimmicks and elaborate entrances.
Against the run of play entirely, Real Sociedad had their equaliser when a cross from Idriozola found Kevin Rodrigues free at the back post and he drove a volley at Keylor Navas.
The 'Yellow Submarine', managed by ex-Gunners Unai Emery, will go into the second leg on top, but facing the prospect that just one unanswered concession will send them out.
He won a penalty after Lindleof took him out of it in the penalty area, which Casemiro buried it. It ended 1-1 in a game that was hard to gauge due to the number of changes on either side.
Pogba's excellent finish from outside the box eventually stood following a VAR review to check whether Henderson's long clearance to Rashford had curled out of play and then back in.
The home side added a second on 53 minutes when Hwang Hee-chan picked out an easy finish for Matheus Cunha at the far post and the Brazilian then turned provider when Craig Dawson poked home a low cross.
The visitors failed to clear a corner and the ball fell for Haaland at the back post to smash home a fierce first-time strike that Pickford got a hand to, but could not keep out.