The decision which EAP type(s) to deploy on your eduroam IdP depends on several factors:
Here is a break-down of anonymous outer identity support for some popular EAP types:
|EAP-Type||Support for anonymous outer identites|
|EAP-TLS||support in protocol, but not typically available in supplicants|
If the EAP type allows for the use of outer identities, it is a client device configuration option to either make use of them or not; there is little you as an IdP can do to force the use of anonymous outer identities (except for providing and encouraging the use of pre-configured installers which will then make all the necessary settings on the client device automatically).
Choices depending on the envisaged devices
The landscape of wireless-enabled devices is rather heterogenous, and support for EAP types varies. Ideally, you should survey which types of devices you should come to expect among your user base, check the capabilities of these devices, and make an informed decision regarding the EAP type of choice.