First of all, confidentiality and credibility are the basic professional ethics that formal agencies must first achieve;
Secondly, if you want to apply for a patent, you must not only consider the price factor, but also consider the writing Quality, subsequent service quality, subsequent fee collection, etc.
Generally, formal agencies will have relatively professional patent agents. Experienced agents can better protect your patent and reduce subsequent invalidity, infringement and other problems caused by patent quality.
For more formal agencies such as Beijing Light Innovation and Fasite Patent, you may wish to call and inquire first. After shopping around, you may wish to visit in person.