Next steps

I have grown these two silk mimosas and jacaranda from seeds, they are roughly a year old now, they have survived their first winter nicely and they started growing a lot again so now I have some questions on what to do next as I want to keep them around this size but with a thicker trunk:

– Are they growing too much for a bonsai?

– Are the pots too big and should I move them to something smaller to stop them growing too much?

– Shall I trim the next sprouts to promote a thicker trunk instead?

Thank you all in advance!