During the installation process, you can choose a role that you wish to set. You cannot change role afterwards.
Is there a minimum required upload speed/latency for running a node?
Any computer can likely handle the node running if it has a decent and reliable Internet connection.
The core software is not even theoretically capable of ensuring quality of service (QoS) in a decentralized P2P network.
The way to tackle QoS issues in Core is only through the Rating system. In case the quality of service will be low ( latency, speed, availability, etc.) - it will affect the Rating