Hey,
I've talked with Apple Support to get a trackpad for my green 2021 iMac and they say that I can order it with USB-C, so i think that means all the accessories you want to order for your M1/M3 iMac are now USB-C, so you don't have to upgrade for these accessories (especially as the back colour for the green M4 iMac is HORRENDOUS.
Have a good day!
I've talked with Apple Support to get a trackpad for my green 2021 iMac and they say that I can order it with USB-C, so i think that means all the accessories you want to order for your M1/M3 iMac are now USB-C, so you don't have to upgrade for these accessories (especially as the back colour for the green M4 iMac is HORRENDOUS.
Have a good day!