Very approximately, a dinner fork is 20cm, a regular dinner plate is 28cm.

The fork when laid on the plate should just lap into the 'border' area, rim/lip [the raised outer ring that you don't put food on.

That makes the plates in your pictures smaller than regular dinner plates or soup plates [26cm], but larger than side plates [20cm]. As they don't have a traditional rim/lip but curve up rapidly at the edges, I'd say they're about 22cm. The fork would just sit inside without any overlap.

Personally I think they make the food look crowded, especially the top one. The bottom one feels like the plate is too deep for the food, the lighting makes it look sunken. For both I'd have just thinned things out towards the edges a bit & tried to lower the shadowing.

There are arguments for crowding the plate/bowl - noodles, for example which will always flow to fill the space, though here there is still a distinct margin & the highlights, broccoli, peas, etc strategically placed

https://500px.com/photo/291415211/Noodles-stir-fry-with-vegetables-by-Vladislav-Nosick?ctx_page=11&from=gallery&galleryPath=21002029&user_id=10743317

but there are arguments against - allowing the grains to thin out to the edges in this more homogenous meal

https://500px.com/photo/272902675/Couscous-salad-Tabbouleh-with-pomegranate-seeds-by-Vladislav-Nosick?ctx_page=16&from=gallery&galleryPath=21002029&user_id=10743317

or more noodles - this one beautifully spaced

https://500px.com/photo/1001491999/Japanese-Ramen-Noodle-Soup-With-Chicken-by-Vladislav-Nosick?ctx_page=1&from=popular

This one, conversely, doesn't work at all for me; crowded, messy with food overhanging the edge, clumped, unappetising, blurry, (I could go on ;)...

https://500px.com/photo/124225089/Mushrooms-with-noodles-and-sauce-by-Christian-Fischer?ctx_page=2&from=search&ctx_type=photos&ctx_q=noodles

Regarding the OP's comment -
"The objective of the shoot I'm creating is to have the plate inside the scene so it shouldn't be cropped which has led me to the conclusion that the bigger the plate, the smaller the food inside the plate will seem to the eye. In the photos I have attached in the original question, the food inside the plate seems larger than what I've been able to achieve in my own shooting..."

I wouldn't use the photos you posted as a definitive guide. They are completely crowded. Not just the servings themselves, but they seem desperate to get as much in close-frame as possible, very much at a cost to how appetising it all looks.

They look like they're selling you a café lunch, not a fine dining experience.