Seventh-day Adventists traditionally are lacto-ovo vegetarians (eating dairy and eggs but no flesh foods). Some very conservative Adventists are dietary vegans (no animal products at all). When I was growing up, they were called “strict vegetarians.” Adventist non-vegetarians eat beef, chicken/turkey, and fish with fins and scales, but do not eat pork or shellfish, among other flesh foods described in Leviticus 11 and Deuteronomy 14. There is a wide spectrum of opinion about vegetarianism/veganism.
Start with this comprehensive overview (for vegetarians and pescatarians):
10 HIGH-PROTEIN LOW-CARB VEGETARIAN FOODS (PROTEIN CHARTS)
Ellen G. White and Vegetarianism
Food For Thought: Meat-Based Diet Made Us Smarter
How Safe is Eating Meat?
Meat Alternatives Explained: Tofu, Tempeh, and Seitan
Red Meat Causes Cancer?
Red Meat Does Not Cause Disease