The KN95 is the Chinese standard and was used to good effect in Wuhan for example. KN95 should be tested and approved to the Chinese GB2626 standard. This is a good level of certification and these masks filter out at least 95% of particles including virus and most pollen. N95 is the US equivalent and no different performance or application except that is as lot harder for Chinese firms to find certification houses approved to validate NIOSH (US) standards. It is usually possible to check the certificate number on the certification company's web site. It will give you the name of the genuine owner of the test results. If you suspect the certification company is fake, you can check the certification company with CNAS, China National Accreditation Service for Conformity Assessment. There is a "White List" of certified firms but it is out of date so your supplier may be legitimately certified. The Chinese KN95 and type US N95 do not meet EU standards for working use with hazardous substances but as virus filters for use in public spaces and confined places with a lot of other people they exceed the performance of flat masks when they fit to the wearer's face (they are designed to make this easy for most adults).
The EU FFP2 filtering facepiece is part of a series of standards to protect people working with hazardous substances. In terms of water based droplets and aerosols it has the same capabilties as the KN95/N95. However, the standard also demands that masks filter out oil based particles. KN95's and N95's are not designed to do this. FFP respirators require at least one layer to be oil filtering. This material is harder to come by in China and more expensive. Masks are typically 5 layer, sometimes 4. The FFP1 grade is not suitable for antivirus protection and the FFP3 grade provides a level of protection suitable for intensive medical use. In the European Union, only CE marked FFPn respirators can be used for protection in the appropriate woring environments. Respirators that have not been validated with a CE mark or K95/N95 are not suitable for working with hazardous materials.
3M has a more technical comparison of standards than is written here. Governments, such as the UK have based their advice comparing respirators on this 3m technical bulletin. https://multimedia.3m.com/mws/media/1791500O/comparison-ffp2-kn95-n95-filtering-facepiece-respirator-classes-tb.pdf
Respirator manufacture is a new industry. ISO 9000 is uncommon as few firms have been in production long enough to qualify.
Volga Trader is an agent for a Chinese supplier of KN95 masks. FFP2 masks are awaiting certification. Advance orders can be taken. However, for non clinical antivirus use by the general public, KN95 is suitable and available now.