Im not sure when I should Transplant...

So Im new to growing. I germinated a few seeds and got two plants growing in one cup. when should i transplant. theyre a week old and growing rapidly overnight it seems like. theyre sativa seeds from saved up sacks of schwag. I really plan to buy equipment but being its summer here in AZ i've started by growing in my window and my first few plants will be grown a combination of outdoor for light and indoor for seclusion and to be kept from the dark. I havent tooken plants outside yet. theyve been growing in my window jus t fine. Any tips. I want these to turn out decent. First time. Help? Tips. Anything. Please. It'd be much appreciated. Thanks in advance.

id separate them now or in a few days at the most, the roots will start getting tangled if you leave it any longer than that. wash and rinse your hands really well before handling them too.
give them each their own cup for a week or so then go to a 6" pot for a few weeks, this will help build a good root mass and make better use of the available space in the pots.
make sure you dont over water them, this can stunt or kill the plants, feel the weight of the pots and only water when theyre light. test a dry pot and compare to it so you know.
add perlite to the soil that youre using to aid in aeration and drainage.
using like 30% or more perlite will allow you to water more often with less chance of over watering too.

Thanks. I appreciate it very much. I just have one basic question. Being as the plants seem to be so close together in the cup if the roots are ALREADY tangled which i wont know til i dig it up, should i leave it be or is there a process to untangling the roots without significantly risking the life of one or both plants?

just be gentle with them and try not to touch the roots much if you can help it.
could get a bucket of water and submerge the roots in that and they should separate fairly easy then.