I guess you can submit 140 485 together
since the day your 485 is submitted, you status changed to AOS
it is a legal status for you to stay in the US until your 485 is completely
denied
after 2-3month, you will get an EAD, in case your i140 is still pending at
that time, you can use EAD to look for job
the bad thing is that if you i140 is denied, you are out of status
imdediately. And you are no longer eligible for F1/f2 status