Since mine is the more affordable type, it is devoid of a thermometer

Ninja IG601 vs IG651 Food products that are at or below 35 degrees F (1.5 degrees C) will not register on the thermometer. To signal that the probe has to be inserted, it will flash on and off. When cooking directly from the freezer or refrigerator, you must first let the food warm up before attempting to regulate the temperature. The instruction book needs to mention this. However, they don't. I adore everything about it except from that.  I wouldn't pay the additional $150 for the thermometer and a few other presets on the device. A more accurate external thermometer could cost much less. 

This is what makes it possible to use it as a griddle. The bottom heating element continues to function when the lid is raised without the requirement for the upper air-frying heating element.  I don't believe so, no. It is rectangular in shape, larger than the original Ninja, and has a larger cooking surface, both of which restrict what can fit on it. If the larger pizza is square or rectangular, your chances are better. However, they are excellent for French bread pizza. With this model, you can griddle and cook with the lid open or closed. The FG551 can only cook with the lid closed and is devoid of a griddle.  It is oblong and has a 9 by 12 inch size. 2. Dehydrating clock range A dehydrating option is there, but I've never used it and don't know how it functions. 3. Since mine is the more affordable type, it is devoid of a thermometer. The thermometer-equipped model costs $100 extra.  I'm not sure whether I comprehend the question. This Ninja Grill came with everything I needed when I got it. To utilize it, I didn't need to purchase anything else. If you decide to get one, I'm sure you'll be happy with it. 

The feature doesn't come with any guidelines, recipes, or extras. neither for the roasting or baking purposes. What precisely do they think?  No, just some soapy water and a rag will do. You can take out the screen or oil filter and wash it in the dishwasher. Avoid using harsh chemicals on this.  12 Grilled barbecue: High-intensity direct heat is used by the flat-top barbecue griddle to cook food that grills cannot. To accomplish this, it engages the grate. Precise temperature controls provide quick, consistent cooking without hot or cold spots. Food gets seared, sizzled, and crisped on the Ninja Foodi XL Pro grill and griddle. Indoor grill, griddle, and air fryer. In addition to the Ninja Foodi Smart XL Griddle & Grill, this set includes a 4-qt. Crisper Basket and Quick Start Guide UP TO 75% LESS FAT*: Air fry crisp with up to 75% less fat than deep frying with the included 4-qt crisper basket (*tested against hand-cut, deep-fried French fries). Family-sized capacity for XL: Up to six steaks, main courses, and sides can all be cooked on the grill at once. A flat-top BBQ griddle can be used to cook a whole serving of nachos, four sandwiches, or six pancakes. UP TO 75% LESS FAT: Air fry crisp with up to 75% less fat than deep frying (tested versus hand-cut, deep-fried French fries) with the included 4-qt crisper basket. NINJA'S STRONGEST GRILL: For better char-grilled results, an independently powered 500F grill grate generates direct, edge-to-edge high-heat searing. (Based on the grill grate's direct heating element in comparison to grills from the FG500 series.) BBQ GRIDDLE No. 12 This flat-top griddle interlocks with the grate to harness its direct, high heat, and it can cook foods that grills cannot. Precise temperature controls allow for quick, consistent cooking with no hot or cold spots. Smoke Control System: To keep smoke out of the kitchen, our chef-recommended grilling techniques, a temperature-controlled grill grate, a splatter screen, and a cool-air zone all operate in concert.