Purely surge protection?
Lightening, surge, everything was like 15k. Can't remember what the classes mean.
Classes define a minimum for human safety. Grossly undersized protectors can create house fires.
No protector does protection. Best protection is a hardwire connected low impedance (ie 'less than 3 meters) from each incoming utility cable wire to earth. Some utility cable wires cannot connect directly. So we do a next best thing. Make that same connection with a protector. A protector only does what a hardwire would do better.
Other protectors that do not and could not possibly have an earth ground (ie class 3) do not claim to protect from typically destructive surges. So yes, to have protection from typically destructive surges requires a class one type ... connected low impedance (ie a wire with no sharp bends) to single point earth ground.
Lightning is typically 20,000 amps. So a minimally sized 'whole house' protector is 50,000 amps. Because any suffient protector must earth direct lightning strikes. And remain functional.
What should have everyone's attention is price. Protectors that do not claim such protection are most expensive. One 'whole house' protector costs tens or even 100 times less money per protected appliance.
Spend little time discussing protectors. Spend most time on what actually absorbs hundreds of thousands of joules. Those plug-in protectors, that only absorb hundreds of joules, do what? Most critical is quality of and connection to single point earth ground ... where hundreds of thousands of joules must be absorbed so that nobody even knew a surge existed.