I don't think there's any stand out candidate for us, but they'd probably be my favourite two for different reasons.
Tuchel out of the more proven / experienced managers available. McKenna out of the more inexperienced (at high level) gambles.
Obviously McKenna is still relatively new to first team management, so in that respect he'd be an even bigger gamble than the likes of Potter or De Zerbi. However, timing wise, he's very much on the up and he already knows the club well.
As regards which of the two? My heart says McKenna, but my head says Tuchel as he's as close to an 'elite' level manager that we could realistically get this summer. Though I'm worried that he's on his way down, similar to the likes of Mourinho and Conte, rather than still at his peak. That's probably why we could maybe get him in our current state. But if we can't get an actual 'currently elite' manager this summer, then maybe we should go for one of the up and coming managers on their way up rather than an erstwhile elite one in decline (i.e. the Schweinsteiger / Casemiro's of managers)?