Dynasty draft question!

How do you do your drafts on ESPN? We have 30 keepers so I assume if you keep 15 you can’t draft for 15 rounds? Does it effect pre draft positions? Meaning if you have Joe going first because he was last place last year but he kept 29 players does he not pick Til the very end of the draft? What about setting up position drafts… for example I pick Kamara in the 5th round last year can I make it so I miss that round if I keep him? Or just bag it all and do an email offline draft?