Ideally, for each sideboard card you introduce to a deck, you take another from the main deck to keep your deck at 60 cards and thus keep it efficient
The two new starter decks are designed to play out of the box and feature a combo of two Ink types: Ruby & Sapphire and Amber & Emerald
Last year, I got to talk about the Warhammer 40,000 Commander Decks
Not a bomb, but it did work in the Domain archetype, as it was able to get you the dual lands to boost your Domain count
As for the downsides, it only untaps one of your creatures and is a sorcery
Still, the rewards for successful drafts include both gems and packs, so if you can earn your way into a draft using coins, then you'll have more packs to open, which refers back to method one