Abek42:
Out of curiosity, what exactly is the deal with the 1MHz and 8MHz?
From the factory, the processor is configured to run from the internal oscillator divided by 8. The "divided by 8" can be changed to "divided by 1" by changing the "fuses". Conveniently the Arduino IDE will do all the work. Select the board (e.g. ATtiny84 @ 8 MHz) then click Tools / Burn Bootloader.
I mean, how do I know what chip to use with the 1MHz and which one to use with 8MHz?
Start with the target running at 8 MHz.