Alright, I think, I figured it out. Please correct me if I'm wrong, though.
Did a bot match to replicate the scenario. Had my Valkyrie and Sparky had some zombies, two Mystical Reflections ready to cast. With a token trigger on the stack for two tokens, I cast the first MR on the Valkyrie, let it resolve, then cast the second MR on a zombie, then let everything resolve. I chose replacement effect #1, then chose #1 again, then had to choose again, took #1 yet again. Got two zombies.
What I gather from this is, that the first two replacement effects refered to the first token, and the rest to the other token. So the replacement effects are presented like this: all effects regarding one creature, in order of creation, then all effects regarding the next creature, in order of creation. To get my Valkyries, I have to choose second, and then last, thus choosing zombie for both tokens first, and Valkyrie second. Last copy effect wins, and Valkyries enter the battlefield.
(Note to the moderators: please don't move this to the Arena forum. That one is deserted and moving the thread there will make it go unanswered. Hence why I posted this here in the first place.)
Quick question for those versed in the intricacies of MTGA. Because I had this come up in my last game, and couldn't figure it out. A wrong series of choices would have cost me the game. I ended up guessing, and luckily I guessed right at least once, and was able to win. Anyway, here's the problem:
I had my Righteous Valkyrie on the field, and the token trigger from Omen of the Sun was on the stack. I proceeded to cast Mystical Reflection on my Valkyrie at that time, so that I would get 2 more Valkyries from the trigger. My opponent let it resolve and then cast his own Mystical Reflection on one of my human tokens already on the field. We passed, and the trigger resolved. Now the issue: I was presented with 4 choices of replecement effect, all from MR, for each token one for Valkyrie and one for human token, all looking exactly the same. Now how do I tell which one is which? I want Valkyries, not humans.
I ended up choosing first the third option, and on the repeat the second out of three remaining, which settled the order, so my two choices refered to different tokens. I got a Valkyrie and a human. Is that enough information to figure out the right order if that happens again in the future? And what is that right order of choices?