Is a fixed 4x enough scope to varmint hunt with a 22-250?

Yes, but it limits your effective range. I'd prefer an 8X or at least a 6X for the .22/250, if you are going to use a fixed-power scope.

For varmint hunting I'd much prefer a 3-12 variable scope.....but you can do it with iron sights if you wish.

It'll do the job of course, but really the effectiveness depends on the distance you'll be shooting at. 4x (for me) is perfect for close range shooting, but if you want to reach out there beyond 100 yards you may want a higher magnification. A variable would likely be a better choice with a wider range of applications.

I agree 4x wouldn't be the best for a varmit setup. I would go with a higher fixed probably an 8x but a variable of 10-12x would be better suited imo.

I am planning on putting the scope on an encore 22-250 pistol. Pistol scopes are wicked expensive for a good one. The fixed scopes are much less but I don't want to be too limited.

The .22-.250 is known for shooting long range over 200 yards . A fixed 4 usally has too large of crosshairs to shoot varmits at that range . With it on a contender it may be all you need