Most autos have the same potency as photoperiod plants. Trust me, you won't notice the difference. Every time I smoke my skunk mass I get too high and get all paranoid lol. They have come along ways in even just the last year!
i know man, prime is awesome and totally worth it! I would look for your soil locally, or see if a local nursery can order it in. It's only $12-14 a bag, the rest is for shipping. I can honestly promise you if you get airpot a, you won't be disappointed!
generally speaking, all strains need the same nutrients. Supplements such as calcium and magnesium can vary a lot depending on strain. Don't overthink nutes though, go simple and cheap. I love dyna gro products. Also, look into a digital soil ph meter instead of those drops from GH. Take it from me, it's a pain to figure out what ph it's at. It's like I go color blind as soon as I need to see subtle color differences.
I would order it all from amazon as you really can't beat the prices. I've looked all over the place and amazon has always been the cheapest besides for soil.
if you need a link on amazon for a cheap, reliable ph meter, just let me know and I'll track it down for ya!
Oh and if you want a killer, high yielding auto, look into think different from Dutch passion. Some amazing stuff! Google" Tavidude think different" it's on here and he really shows the strains potential! Good luck man and feel free to pm me about anything, I'll help where I can!