There are a bunch of notifications available, see UI > Notifications - these are the standard 'simple' notification you mentioned, i.e. popping up when something was collected and can automatically close. The notifications can be queued or show whenever they are added (i.e. allowing multiple at the same time).
For the bigger notifications for new items, you could handle this via inventory schematics (see Inventory > Inventory Settings). The schematic can show a dialogue (e.g. using Selected Data Question Dialogue node to use the item's content information) when adding something to the inventory. Only showing it the first time has to be handled manually, e.g. using variables to store some flag and check for it - best way probably using the GUID of the item via Store Selected Data GUID node.