The phrase "are usually complex and" is correct and usable in written English.
It can be used when describing something that typically has a complicated nature or structure, often followed by additional information.
Example: "The systems we use in our research are usually complex and require specialized knowledge to understand."
Alternatives: "tend to be intricate and" or "are often complicated and".
The chemical reactions are usually complex and involve hydration, oxidation, and carbonation.
Any kind of changes at a nuclear power plant are usually complex and cumbersome, and this one — moving the bundles of fuel rods 300 feet — was even more so.
Their configurations and joints are usually complex and require a high level of craftsmanship to assemble.
Bioassays are usually complex and display poorer reproducibility than physicochemical tests such as HPLC assays.
However, software applications for detailed spino-pelvic analysis are usually complex and not applicable to routine clinical use.
The energy systems of a typical contemporary building are usually complex and may contain several subsystems deployed independently of each other.
The deformation is usually complex and relies on several interdependent rhelogical and morphological parameters.
This is particularly useful when considering the effect of root reinforcement because the critical slip surface is usually complex and unknown when vegetation is present.
As a result, the most successful variants related class of "segment-based" methods [10, 11], and the optimization is usually complex and extremely computation intensive.
However, the effect of each parameter on the overall performance of the catalyst is usually complex, and the catalyst designer is often faced with a tradeoff between activity, stability and ease of activation.
It needs to be noted, however, that the transcriptional activation of genes is usually complex and it is conceivable that NF-κB pathway cooperates with other signaling pathways in the transcriptional activation of some genes.
