Perlite is almost never a good additive for mushroom growing. Mycelium does not colonize perlite well also attracts a lot of contaminants  And substrate is any growing medium you use to grow mushrooms. The bulk substrate. People use non nutritional sub's quite often for example some people swear by coco coir. Rez effect is exactly like bulk you just use a much higher spawn ratio. About the only think perlite is good for is lining the bottom of an fc to maintain humidity.