Can i change both wheels on a 27.5 to a 26 rim on giant e bike 12 speed as need bike slightly lower

[Hanging on for dear life]

I no its only about a inch and would i have to change forks as well

 

[PedalUma]

Given that you have disc brakes you should be fine. Include some photos. Are you bike shop adverse? Do you have the tools?

 

[Hanging on for dear life]

Yes have a all sort of tools as strip and grease and clean bike and haven't been to a bike shop for advice