You can chose legacy or segwit, even within the same wallet to have two divisions and to be able to view overall balance or the balance of the separate formats.

I am pretty sure that if you seed a trezor with a wallet that you already have, then it will keep the same format, and you can view each of the locations... and move coins between segwit or legacy addresses too, to the extent that you feel more comfortable with one versus another or some combination.