General refactoring and improvements (#373)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

ultralytics/yolo/v8/classify/val.py

@@ -48,8 +48,8 @@ class ClassificationValidator(BaseValidator):
 
 @hydra.main(version_base=None, config_path=str(DEFAULT_CONFIG.parent), config_name=DEFAULT_CONFIG.name)
 def val(cfg):
+    cfg.model = cfg.model or "yolov8n-cls.pt"  # or "resnet18"
     cfg.data = cfg.data or "imagenette160"
-    cfg.model = cfg.model or "resnet18"
     validator = ClassificationValidator(args=cfg)
     validator(model=cfg.model)