I suspect the reason you get different answers is because it's different for everyone! What specifically do you mean by raw greens? Lettuce? (Sorry, I think the terminology for quite a few veg is different in the UK from the US.)
I used to be able to tolerate lettuce, cucumber, etc. raw as long as I kept it to small amounts - I didn't even need to blend it. However, now I have an ileostomy and it gets blocked at the slightest thing. I can't have anything like that now, no matter how well it's blended. Since you have narrowing of the intestine, I think you should also err on the side of caution here, as that sounds similar to the problem I have with my stoma - the stoma opening is too small.
I don't have a juicer, but I have a blender and I use it for cooked veg like sprouts, broccoli and a few other things. One thing I have found useful is, after blending vegetables, I put them in a sieve and mash them through with a fork. Whatever makes it through the sieve I eat, anything that doesn't, I leave. Again, this is only since the ileostomy.
So really you have to experiment to see what's ok for you, but if you are risking actual blockage, rather than just a temporary deterioration in symptoms, you may not want to experiment too far. Before the ileostomy, I ate moderately low-fibre and I knew that if I ate too much it would just cause me to feel uncomfortable and make the diarrhoea worse, but it was more the overall amount of fibre I consumed over consecutive days that was significant rather than any particular food. Now with the ileostomy I am strictly low-fibre, as eating it causes a blockage. The quantity of fibre eaten is still an important factor, but the foods most likely to cause blockages (some veg - in particular lettuce, cucumber, and other salads, - fruit skin, pips, seeds, nuts, dried fruit) I avoid altogether because even a small amount is a risk.
Have you had problems with fibre already and how severe were they? Knowing your levels of tolerance will help you know if it's worth experimenting with a blender, but since you have narrowing, I would suggest the juicer would be safer, especially if you've already found small amounts of fibre to give you problems.