Blackjack variations like Spanish 21 and Vegas Strip alter gameplay by modifying specific rules, which can affect strategy and odds. In Spanish 21, all 10-value cards are removed from the deck, increasing the house edge but offering more favorable player rules, like bonuses for certain hands and late surrender. Vegas Strip Blackjack typically uses four decks and features more standard rules but allows for strategic differences, such as doubling down on any two cards and re-splitting aces. These variations require players to adjust their strategies based on the unique rules that influence their decision-making and potential outcomes.