Hi there just read through the thread and congrats on getting the 125 over the biorb really good choice
Its good to see you went through a proper fishless cycle as well how long did it take in total to get your double 0?
From the stock plans and fish you have mentioned you put up this is what I would do.
6 Platies - (all male)
6 Guppies - (all male)
10 Cardinal Tetras
12 Corydora Catfish - either all 12 of one species like all bronze or 6 of one and 6 of an other.
Right so my reasoning for this list, I put platies in instead of mollies as they grow smaller than mollies and are also less problematic. However now that you have your mollies dont worry it should work out I just plan stock lists avoiding any potential issues but its sometimes down to the individuals. I also upped the number of guppies just to add some more in really. With livebearers I would always stick with just males, this means that you are not overrun with fry which could happen with your mollies so something to learn about there. The main issue with livebearers now is that many LFS wont take fry in because they have so many already so make sure you find an outlet for them as your 6 mollies could soon turn into 20 and then 40 and so on and so on.
I also swapped your neons for cardinals, cardinals are much hardier and bred from a better stock than most neons they get a bit bigger and look almost the same. However if you wanted to have a look at some other tetras as well there are plenty that will work in that tank like flame tetras, rummy nose or green fire tetras.
I also upped your cories to 12 from 3, while some people will say the minimum is 3 its not the absolute bare minimum is 6. And thats like of one species like just the bronze or just the peppered etc so like I say I put 12 in because a big group of cories are a fantastic site but if you want to mix it you could get like 6 panda cories and 6 sterbai cories for a bit of variety
On that list you would still have a bit more room in your tank for some feature fish though with the bigger mollies it would be slightly less.
Hope thats helped
Wills