The phrase "are characterized by a mix of" is correct and usable in written English.
You can use it to describe the features or qualities of something that includes various elements or components.
Example: "The paintings of the artist are characterized by a mix of vibrant colors and abstract shapes."
Alternatives: "are defined by a combination of" or "exhibit a blend of".
Pummeled by the 1989 earthquake and a catastrophic fire in 1994, the city is struggling to make an economic comeback, particularly in East and West Oakland, which are characterized by a mix of stately but aging Victorian houses, boarded-up storefronts and few commercial services, like supermarkets and bank branches.
These developments, often termed "commercial strips" or "linear commercial complexes", are characterized by a mix of many different types of businesses that often lack any separation from the road, spatial definition, or natural features such as trees.
The programme is characterized by a mix of household level outreach activities with community--level organizational tasks and social mobilization.
Housing in Stockholm municipality is characterized by a mixture of multi-dwelling buildings and single-family homes each representing a mix of ownership and tenure-types.
Large and small private clinics and solo clinics are characterized by a variable mix of walk-in and family practice in a private context.
These desakota regions are characterized by an intense mix of agricultural and non-agricultural activities that often stretch along corridors between large city cores.
Complex manufacturing systems are characterized by a large number of products, an over time changing product mix, sequence-dependent set-up times, unrelated parallel machines, a mix of different process types and internal and external disturbances.
The mixing behaviors are characterized by a particle-scale mixing index.
In developing countries, traffic is characterized by a wide mix of vehicle types that differ considerably in their dimensions and performance capabilities.
The relationship of apixaban dose with exposure was characterized by a nonlinear mixed-effects ("population") compartmental model using NONMEM (version VI, level 1.1; GloboMax LLC, Hanover, MD).
