Welcome to the community!
As already mentioned, Fido does not currently offer any 5G services. However, any 5G-capable phone sold by Fido will work on their LTE and '3G' networks. If you wish to access 5G services, you would need to switch to one of the Parent providers (namely Rogers, Bell, or Telus) as none of their flanker brands currently offer 5G either. Any price differences to access 5G data would be costs between the different provider levels.
That said, there is speculation that the flanker brands may offer access to 5G for a surcharge at some point (see here). Unfortunately, that notion currently remains conjecture. No one here would know if or when that might happen. Any update on 5G access would be announced on Fido.ca.
Hope this helps 😀