Does a 1000 Joule Surge Protector have enough energy to protect a gaming PC?

Power strip ones are rated at 4500 to 6500 joules.

Surge protectors have no energy. Their ability to shut off quickly enough does the protection.

It is always best to unplug the device during a lightning storm

Yes, it has enough.

Surge protectors are usually only needed where there are problems with the electricity supply, or a lot of heavy equipment being switched on and off all the time, as in some factories.

It does not do any harm to use one, but a plug-in device will not protect against such as a nearby lightning strike...

They work by partially shorting out the power when a high voltage "spike" occurs. The joule rating is how much they can absorb before failing. 

One with 1000 Joule rating would just have something like three of these (rated at the appropriate voltage) connected across the supply, and a fuse to disconnect the supply if they fail and short out.

https://uk.rs-online.com/web/p/metal-oxide-varisto...

Surge protection is not a function of an outlet strip HAVING energy;    

it is a matter of how much energy the MOVs in it can ABSORB before they fail. 

The more joules, the better.      

In general, 1,000 is far too little. 

Go for at least 5,000. 

Your best option is to purchase a battery backup at Walmart for about $75 they have built-in surge protection and there is a battery in the system and a line stabilizer it's better than just a simple surge protector