SFDX projects and source format and CLI useage
Gearset CI only supports SFDX source that follows the SFDX project template structure (e.g. force-app/main/default/classes and so on). However, SFX CLI doesn't mandate that structure.
SFDX allows you to group metadata by function or logical group (so you can combine metadata in any way that makes sense to you) . We have many projects like this that gearset cannot deploy.
Are you referring to unlocked packages or is this something different?