With RftG and both expansions should one draft all cards out while playing with 3 persons only? So every player would have a deck of 65 cards (leaving 5 cards undrafted). Or should you rather limit the deck size to 40 cards? This would mean you do 8 draft rounds reagardless how many players you are.
Draft all cards out with 3 players and both expansions.
From the TGS rulebook:
Repeat, drawing five cards, selecting one and passing the rest right. Continue, alternating directions, until players are unable to draw five cards apiece. Remove the remaining cards from play.
From the RvI rulebook:
The drafting variant introduced in The Gathering Storm, with the additional start worlds and game cards from this expansion, now supports up to five players (with no rule changes).