Here are two decklists I've won tournaments with a Red-White Aggro Burn deck and an Azorius Control deck, each with vast differences in the number of cards I played in their sideboards: Boros Burn | Modern | Roman Fusco, SCG IQ/1st Creatures (12) 4 Eidolon of the Great Revel 4 Monastery Swiftspear 4 Goblin Guide Instants (16) 4 Lightning Bolt 4 Lightning Helix 4 Boros Charm 3 Searing Blaze 1 Shard Volley Sorceries (12) 4 Rift Bolt 4 Skewer the Critics 4 Lava Spike Lands (20) 3 Mountain 4 Sunbaked Canyon 4 Inspiring Vantage 3 Bloodstained Mire 2 Scalding Tarn 2 Sacred Foundry 2 Fiery Islet Sideboard (15) 4 Smash to Smithereens 4 Skullcrack 3 Kor Firewalker 2 Path to Exile 2 Searing Blood With the Burn deck being a dedicated strategy of every card trying to deal three or more damage to my opponents, my sideboard options were very limited
Either your opponents have to answer your board again or you are probably going to win in short order
Abzan Falconer, Damning Verdict, Duskshell Crawler, and Master Chef add a super effectiveness to your strategy
MTG Deck Builder: Generate your next Commander deck with ease using AI Unleash the Madness: Let AI Build Your Magic the Gathering Commander Deck
Like the Windshaper Planetar, Sigardas Vanguard can mess with an opponents combat, but it can also buff your own combats, too