Normal 22LR rounds are ~38 grains. You're going to get some nice velocity out of a 20 grain round if the powder charge is the same.
I have a few 22LR pistols (some revolvers and some semi auto) and a few rifles (some bolt action and some semi auto). I standardized on Federal Game Shok 38 gr ammo because different ammo will behave differently - use the same ammo and everything is more predictable. Probably doesn't make much difference unless it's a shooting competition, but I'm picky I guess. Point being, if you go to this 20 gr lead free, you will need to sight in your gun for it.
I am jealous. I'd love to have access to a farm over run with squirrels. If you need any help......