To me, 20 grains isn't worth the effort in itself. But if you were to combine that with something like adding 5# of draw weight or a faster bow then it's measurable.
I made an arrow speed calculator the other day for people to play around with. It's based on a good sized dataset with actual chronograph data at varying lengths and weights. I find it a little more accurate than others out there, but none are perfect. This one lets you detune the IBO so it's closer to reality. Most bows I find are about 5% lower than advertised.
To me no. If it was as simple as put a different field point on the front than ya sure. But if you aren't changing anything other than the weight it's not worth it. And like asked above what is your fps now?
Only you can answer that question. What is the main driver for you wanting a faster arrow? There are some pretty easy ways to cut 20 gr without changing arrows. Cutting them shorter, fletching with lighter fletchings, or using a lighter broadhead would be the easiest.
One thing to consider if shooting fixed heads is that once you start shooting over 280fps they become much less forging and groups typically open up unless you are shooting with near-perfect form every shot.
I say go for it. Certainly wont be a huge difference but I find the more I mess with my bow, the more I learn This time of year is the best time to learn. If you ask this question mid August I would have to agree with everyone above who says just leave it alone.