I use 100% coco no perlite. If it is well drained, and it will be in fabric bags, it is impossible to overwater. IMHO, adding perlite just increases the frequency that you WILL need to water. some swear by it
however, be aware; coco should be fed to runoff every time once they are old enough for feeding. It is what flushes excess salts and prevents lockout. 10%-30% recommended every time to avoid having to do a freshwater flush and screwing up cocos internal buffer. otherwise, you will likely have bad things happening right when you are in mid bud when you can least afford problems
The runoff should be removed from the tray under your bags after no more than 15-30 minutes to avoid root rot and drowning your plants. Many people, including myself, use a wet/dry shop vac to remove excess water from the tray. Very quick, efficient, and easy using a vac
Coco is actually technically hydroponic, so you do have to feed it every time once it is out of seedling. It looks like soil, and you can hand water like soil, but that is where the similarity to soil ends. Its hydroponic. as long as you don’t burn them, feed to runoff and clean those trays, you can feed as often as you like with no fear of drowning.
its a VERY cool medium. be aware of the specific nature and properties of coco, and you will really enjoy it