"variety of techniques" is correct and can be used in written English. You can use this phrase to describe when different types of methods or approaches are being employed in a particular situation. For example, "The team is using a variety of techniques to tackle the issue.".
Technicians have a variety of techniques for examining composites.
A variety of techniques have been used for carbonation.
A variety of techniques are taught – from confronting an attacker directly, to attempting to distract them.
Executives used a variety of techniques, including falsifying entries in the company's accounting system.
Tire makers employ a variety of techniques to improve the performance of winter tires.
Several start-up companies are already manufacturing graphene, mainly for laboratories, using a variety of techniques.
A variety of techniques can be employed by attackers in this respect.
Since I tried Ludwig back in 2017, I have been constantly using it in both editing and translation. Ever since, I suggest it to my translators at ProSciEditing.
Justyna Jupowicz-Kozak
CEO of Professional Science Editing for Scientists @ prosciediting.com