An HW30 will take down squirrels no problem with a well-place shot at closer ranges. Most of my tree-rat shooting has been in my suburban backyard, so my tuned urban pro is plenty lethal at closer ranges, but I would be uncomfortable stretching it out over 20 yards.
I think for most folks, it's hard to beat an HW95 as an excellent, all-around springer. that's easy to carry (which can be an issue with the HW97 for field work), and has plenty of power -easily enough for small game to 40 yards or even beyond. The HW50 is also popular, but it's not that much lighter than the 95, the cocking effort is almost as high, and it doesn't make as much power. Some really like it, but for me, if I had to buy just one all-around springer, it's an HW95, probably in .177.
Or, if you have some patience, find a nicely tuned FWB124...little less power, but super easy to cock and a delightful gun all around. But going down the vintage gun rabbit hole is more complicated...)
For scopes, you're going to have to get an airgun rated scope for any springer, but an HW95 isn't particularly brutal like some more magnum guns out there. I love the Leupold 3-9 EFR, but a Bugbuster, Hawke Vantage or Airmax 2-7 or 3-9, or a Nikon 3-9 EFR are all very nice, practical field scopes IMHO.