What are the differences from custom managed switch managed?
No, it synonyms.
There are unmanaged switches - filed power, stuck a wire, and it works.
There is nothing to configure and no settings provided.
There are managed switches - there are settings.
What kind of settings does not matter.
There may be and work with VLAN, and aggregation ports, and monitoring, and anything.
And there can be only one thing.
It is necessary to look the specific functionality of the device.
Then whether to pay more for managed?
So do not overpay.
You have certain requirements to the switch.
If unmanaged switch - fully meets your requirements, take it and enjoy life.
If not - look for a switch that fully meets your requirements.
And what are your requirements - no one but you knows.