I am a novice myself so take my advice for what it's worth but from what I have learned this far, putting trees in actual bonsai pots is something you do once the tree is more or less finished, not neccessarily when they are in the pre-bonsai stage. This is because the smaller pots will really limit the growth of the trees whereas keeping them in larger grow-pots will encourage growth of both trunk size and branching as the roots have more room to grow, which is typically what you want. This is of course, unless you feel they are at the right size already. With outdoor bonsai, alot of people will plant the trees in the ground for years just to gain maximum growth before planting the tree in ever smaller pots. But I guess it comes down to where in the development phase you feel the trees are in. If they are almost done or not.
Then of course you also have the issue of when to replant which varies from species to species. I'm only familiar with the ficus if the ones you mentioned, but from what I have read these should be repotted in summer when they are in their growing phase and not during fall/winter.
But like I said in the beginning, I'm new to this myself and more experienced poeple will probably chime in soon but I thought another newbies perspective could be of some value. I know you might feel you want to do things to help the trees, I know I did(and still do to some extent) when I just had started, but many times it's a patience game, waiting for the right time to do things
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