It depends if one talks about Atoms in general or specific models.
The Celeron J4105 (which powers the ODROID H2), is technically an Atom, and it's massively faster than an RPi 4 (2-5x), but I don't know about the Z8300.
Based on Passmark (which is an arbitrary choice), Rock Pi X and RPi 4 may have comparable performance; if that was established, and I wanted a cheap SBC, I'd definitely go with the former.
Correction: as pointed out, the J4105 does not belong to the Atom, but the Celeron family (although the architecture, Goldmont Plus, may be used in the future for Atom), so the comparison is not correct.
The Celeron J4105 (which powers the ODROID H2), is technically an Atom, and it's massively faster than an RPi 4 (2-5x), but I don't know about the Z8300.
Based on Passmark (which is an arbitrary choice), Rock Pi X and RPi 4 may have comparable performance; if that was established, and I wanted a cheap SBC, I'd definitely go with the former.