Hi baobab72,
if the ATC want you to comply with a restriction, don't worry, they will ask you to do so, and if necessary they will also ask you to descend at a specific rate in order to be levelled at this waypoint. Otherwise i assume a standard descent angle (3-4°)
In Nice sometimes the published altitude constraints are not the real one (eg Bordi arrival, FL170 published, FL150 requested by ATC), that's why I've stopped calculating a precise TOD...