[Compact] PropertyDrawer. Makes Vector2, Vector3 and Quaternion display as non-foldouts, like in the default Transform inspector. Attribute in \Attributes, Drawer in \Editor.

CompactAttribute.cs

using UnityEngine;
using UnityEditor;

public class CompactAttribute : PropertyAttribute {

  public CompactAttribute() {}
	
}

CompactDrawer.cs

using UnityEngine;
using UnityEditor;

[CustomPropertyDrawer(typeof(CompactAttribute))]
public class CompactDrawer : PropertyDrawer {

  public override void OnGUI(Rect position, SerializedProperty prop, GUIContent label) {

		EditorGUIUtility.LookLikeControls();
		position.xMin += 4;
		position.xMax -= 4;

		EditorGUI.BeginProperty(position, label, prop);
		EditorGUI.BeginChangeCheck();

		switch (prop.type) {
			case "Vector3f":
				var newV3 = EditorGUI.Vector3Field(position, label.text, prop.vector3Value);
				if (EditorGUI.EndChangeCheck()) {
					prop.vector3Value = newV3;
				}
				break;
			case "Vector2f":
				var newV2 = EditorGUI.Vector2Field(position, label.text, prop.vector2Value);
				if (EditorGUI.EndChangeCheck()) {
					prop.vector2Value = newV2;
				}
				break;
			case "Quaternionf":
				var newV4 = EditorGUI.Vector4Field(position, label.text, QuaternionToVector4(prop.quaternionValue));
				if (EditorGUI.EndChangeCheck()) {
					prop.quaternionValue = ConvertToQuaternion(newV4);
				}
				break;
			default:

				EditorGUI.HelpBox(position, "[Compact] doesn't work with type '" + prop.type + "' (Supported: Vector2, Vector3, Quaternion)", MessageType.Error);
				break;
		}

		EditorGUI.EndProperty();

	}

	private Quaternion ConvertToQuaternion(Vector4 v4) {
		return new Quaternion(v4.x, v4.y, v4.z, v4.w);
	}
	private Vector4 QuaternionToVector4(Quaternion q) {
		return new Vector4(q.x, q.y, q.z, q.w);
	}	

    public override float GetPropertyHeight(SerializedProperty property, GUIContent label) {
       float extraHeight = 20f;
       return base.GetPropertyHeight(property, label) + extraHeight;
    }

}

Lots of extra height in there when it doesn't need to wrap, any idea how to fix?

Yes

// https://catlikecoding.com/unity/tutorials/editor/custom-list/
// https://gamedev.stackexchange.com/questions/122301/how-can-i-create-a-custom-propertydrawer-for-my-point-struct

public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
{
return Screen.width < 333 ? (16f + 18f) : 16f;
}