On my machine anisotropic filtering does make a difference. With it off (i.e. Application Controlled) I get pretty obvious texture artifacts at the edges of the roads on a base as seen from a tank (i.e. a texture that is at an oblique angle to the viewer). With AF set to 8X these artifacts are pushed out to a farther distance (z axis) so that they are almost unnoticeable (at least I didn't notice them until I turned AF off then back on). On my machine AF has no effect on microstutters (I get them with it on or off). I don't think it has much effect on frame rate either, but I can't really tell (it's pegged at the refresh rate of 85Hz).
However, having AF off or on does not make the D-Day strips on the P51B or D look blocky. They look sharp, like in 1701Es screenshot. (The ones on the Spit XIV look bad, but I think that is intentional, i.e. to match hastily painted on strips.) I doubt your problem is AF.