Welcome! This challenge seems like a great idea and I wish you the best of luck.
When it comes to noticing the differences in your two relationships, don't forget that *every* relationship is different. It's ok if they develop at different times, in different ways, and at different rates... in fact that's the only way it could possibly work, because just as no two people are the same, no connection between two people could ever be exactly the same as another. But that's the beautiful thing -- because no two relationships are the same, no relationship can ever really replace another, each person you love is irreplaceable and if they truly love you then you are irreplaceable to them too. Ok, I've gone on enough.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.