I guess that your main concern is not the value of the CONFIG register it is more that you cannot get two nrf24L01 devices to talk to each other. I've just had a look in the repository for the nrf24L01 library and it appears a recent change (version 1.6.0) has altered the default settings for interrupts which will explain why you are seeing a value of CONFIG which differs from that mentioned in the sketch that you found. You could roll the library version back if you really want to see that specific CONFIG vaue.
That sketch, incidentally, has some inconsistencies such as a comment which says the CE pin is pin 4 and also gives it an odd name, directly manipulates it, but uses a hard coded value here: RF24 radio(9, 8);
Maybe start with another tutorial: Simple nRF24L01+ 2.4GHz transceiver demo