Crosman 2240

Hey everyone, new to the forum.
I have a few questions I'm sure have been answered many times, however I've been on google for the past 2 weeks researching everything about my new gun possible. I got myself a 14.5" barrel and a steel breech. I want to get the most power as possible with minimal gas waste. Due to the amount of reviews and recommendations I also plan to mod the valve by chopping off a few threads, using my dremel to smooth out the inside where the threads aren't needed, and also drilling the port toa 90 degree angle. Any other ideas with that mod?

I also plan to get a rear velocity adjuster but am a bit stuck. What is the difference between a regular RVA and the challenger style RVA? Will I need a new spring or can I use the oem one in the gun now? I've read a lot of good things about the disco springs but would prefer to be able to control it on my own unless convinced otherwise.

I'll have many more questions in the future but my last one for now is pellets for hunting..... The whole purpose for this gun is to take on my backpacking trips around Canada for squirrel, birds and I'm really hoping some rabbits too. I currently have the Crosman premier .22 hollow pellets.
My questions are....

Best pellets for small game, and why?
Weight, what's the difference in the weights, they have a huge range. From what I've read lighter is better for longer shots, heavier for shorter. I'd like to keep my shots under 50', ideally approx 30'.

Thanx everyone, I appreciate you taking the time to read and answer. I look forward to the debates lol.

Cheers