I think the main difference between celiac disease and non celiac gluten intolerance (NCGI) is that one has positive tests (tissue transglutaminase, endomysial antibosies, deaminated gliadin peptides, or endscopy) and one has negative tests.
I’m a celiac. When I get “glutened” I will feel run down, get a stomach ache and possibly get arthritic flare-ups, migraines and constipated. Large or repeated exposures may may it worse. I have not found that I react worse now that I am GF, but I think the symptoms may be more noticeable because I am not used to feeling sick most of the time anymore. Before I was diagnosed, I had migraines half the time, stomach aches most evenings, fatigue, arthritis flare-ups often, and my hair was thinning - that was my normal. Now if I get those symptoms, they stand out because they are unusual. KWIM?
YMMV, but I know some with NCGI who had much more violent symptoms than I ever did, and I know a celiac whose only symptom was anemia. It really varies between people.