I mean...Yair has such shit takedown defense and defensive grappling it's kinda pathetic he was ever a contender but the 145lb division is devoid of grapplers and pretty shallow. Yair has a marketable style and nationality that he got to coast on but is the easiest matchup for Aljo by a country mile.
Allen is probably the second easiest, a couple fatal flaws in Allen's game is that 1. He struggles to have the cardio to stand up to high pressure and 2. When guys wrestle him he has solid takedown defense but isn't the best at creating separation or landing meaningful strikes to punish. So I'd say Allen is a much easier stylistic fight for Aljo, much easier to exploit...tougher than Yair, easier than Movsar.
Ortega...well, being 2-3 in his last 5 and being passed around like a cheap whore for champs to beat the shit out of just doesn't make him the most exciting challenge. Plus, Ortegas takedown defense isn't great it's just not often tested anymore because of his notoriously dangerous submissions. That said, I feel like Aljo can pretty comfortably win a decision here just because if he needs the takedown it's always there, he's a great enough grappler to not get subbed. He gets to dictate this fight and has a lot of options because of that, nowhere is Ortega clearly better either.
I'd say quite clearly Evloev is the toughest fight. He's got the best striking defense out of all these guys, the best defensive wrestling, debatably the best cardio. He's the youngest, he's undefeated and nowhere that the fight goes does Aljo have a clear advantage. This would be two rams butting horns as far as I see it. I think Aljo knows this, but it's prize fighting and the bigger name and lower risk opponent is always the best choice. It's obvious Aljo knows this because he's pushing back from the UFCs interest in making this fight.