The cotton must be tight throught the coil...I know many say not toooo tight cause may cause dry hits but to me I always make it tight in order to not cause spitback and I have no problem with dry hits or anything..
u use an rda so u drip/squonk juice so u won't have problem with not enough juice going to the coil anyways...
As u say u have seen many videos so I assume u don't have any hotspots if u use a contact wrap coil cause that may cause spitback or dry hits...
As u say u diy juices and I guess u know u must let it steep for many days depending the flavour....to me at first that was the worst part cause I am not very patient....I always vape simple recipies with one or up to 3 different flavours max in my recipes...
I think the talo rda and any double coil rda has a lot of space inside and single coil must be kinda biggy to give good flavour....in my opinion you should use double coil and u can use thin Claptons in order to be able to vape at low wattage for a double coil cause the pulse is single battery mod....
For example let's say double coil 3x30/38 fused claptons 5 or 6 wraps each coil or anything similar like those thin Claptons and u can vape those from like 40-50watts depending your vape style and airflow...
anyways the thing is that even tho u can use single coil in a double coil atomizer it won't perform so good cause of the large space inside the atomizer and cause the airflow holes gonna be far away from the coil usually if it's just a single coil in middle...while doubles are closer to the sides and the airflow hits them and then bring up the vapor to the mouth
So to sum it up..
Cotton must be tight into the coil to avoid spitback and ofc dont oversquonk
Diy juice takes a little time to find the right percentages to use for every flavour and manufacturer....plus need steeping to make it taste good and strong...
Don't worry cause soon it all will make sence and u gonna find your sweet spot in terms of juices and coils and everything..