Hub upgrade questions with legacy Tradfri bulbs & switches

I have and use the tradfri product line for lights and switches, and I know Ikea has changed their product line to use the DIRIGERA hub and new models of bulbs and devices. Fortunately using the ikea bulbs have increased the "smart" acceptance factor with my family that we now have Echos, and starting on appliances (Samsung smartthings)

Two big questions I have.

1. • since i still have the existing tradfri equipment in the system, does the Dirigera hub run the older stuff too in addition to the new equipment, or do i need to do a wholesale change of bulbs and switches if upgrade or add the newer ikea stuff?
2. • with my family being more accepting of this kind of equipment, does the hub accept other non ikea smart devices in addition to its own, or would there be a better hub choice to support more devices, if i stay with ikea lighting devices, but looking to add things ikea doesnt make (appliances, plumbing, security system)