Designers often mix different types of wood in interiors, but if you have no experience in design, it is better to stick to two types of wood so as not to overload the interior.
Professionals calculate proportions not by formula, but by eye. Moreover, they take into account not only natural wood, but also all elements that imitate it: PVC panels, furniture made of any materials, covered with interior film, quartz vinyl. But furniture made of wood, painted so that its texture is not visible, is not taken into account. When calculating proportions, you need to keep in mind all surfaces, including the floor, furniture, shelves, window frames, lamps and even trinkets on the shelves.
The most harmonious proportion is 70/30. Take 70% oak, using it in engineered floorboards, wall panels and furniture leg trim. And let 30% be grisard – in cabinet panels or in a TV stand.