Question About LCS Technicalities (Relegations)

So I have a question...

The lowest team in the bracket in LCS (specifically NA) will not be auto-relegated anymore, but placed as a lower seed in the promotional / challenger tournament? And is there a potential for new teams to come in after the spring split into the summer split from the challenger series or what not, or does that vary from year to year?

Concerning NA, say, if Renegades is the lowest team in the standing and DIG the second lowest, will they have to compete in a tournament vs other teams to fight for a spot in the Summer split?

Thanks for your help in advance, Monkey