The control of centrifugal Comp. 2

None of the rest of us know the context of your installation, or even what it is that you are compressing, or supplying.

A unitised air compressor on a pallet with integrated controls, needing only connection to external power supply of the correct voltage and capacity and with a single pipe connection to your plant, means that if something ever goes wrong, (1) there is only one vendor for your finger to point towards (no "blame game"), and (2) it is a whole lot easier to rip that entire unit out and replace it with another one.

But, maybe that isn't a factor in your installation, or it isn't a viable approach for whatever reason.

More information = better answers.

Also ask your preferred compressor suppliers what scope they prefer, and why.

No reason to bundle scope along arbitrary lines if the best vendors aren't going to bid to it.

If you are considering single centrifugal air compressors or pairs, the controllers provided by the compressor manufacturers are generally provide good service.

If your system is more complex, third party solutions can provide more optimization. They also require an owners engineer willing to take the time to ensure the setup is, and stays, optimally tuned.

Take some time to educate yourself on the various types of compressors, the optimizations that work with positive displacement compressors are not the same ones that apply to dynamic (centrifugal) compressors.