To determine number of matches, discard tokens will be considered part of vault. So if you have 70 vault size but 10 discard tokens, you are considered to be at 80 vault size and field 3 decks. SG relics are not counted directly here, but if a team which is below 50 vault size but would not be eliminated by transforming SG relics into discard tokens, they will not be eliminated but required to use those tokens to go above 50 vault count at the end of deckbuilding.