A basic Perlin fractal should give you this type of terrain. Just don't have a tiny smallest scale. Make your 'smallest scale' the same as your 'feature scale', and maybe lower the default displacement multiplier.
Try this(copy the entire code and paste with ctrl+v into your node network)...
<terragen_clip>
<power_fractal_shader_v3
name = "Fractal terrain 01"
gui_use_node_pos = "1"
gui_node_pos = "-680 640 0"
gui_group = ""
enable = "1"
input_node = ""
gui_use_preview_patch_size = "0"
gui_preview_patch_size = "1000 1000"
seed = "45710"
feature_scale = "500"
lead-in_scale = "2500"
smallest_scale = "500"
noise_octaves = "4"
apply_high_colour = "0"
high_colour = "1 1 1"
apply_low_colour = "0"
low_colour = "0 0 0"
colour_contrast = "0.5"
colour_offset = "0"
colour_roughness = "5"
clamp_high_colour = "1"
clamp_low_colour = "1"
apply_displacement = "1"
displacement_direction = "1"
displacement_amplitude = "250"
displacement_offset = "0"
displacement_roughness = "0.875"
displacement_spike_limit = "0.25"
continue_spike_limit = "1"
adjust_coastline = "0"
coastline_altitude = "0"
coastline_smoothing = "30"
noise_flavour = "0"
noise_variation = "2"
variation_method = "2"
buoyancy_from_variation = "0.5"
clumping_of_variation = "0.25"
noise_stretch_XYZ = "1 1 1"
distort_by_normal = "0"
distortion_by_normal = "5"
lead-in_warp_effect = "1"
lead-in_warp_amount = "0.75"
less_warp_at_feature_scale = "1"
allow_vertical_warp = "0"
blend_by_shader = "0"
blending_shader = ""
fit_blendshader_to_this = "0"
invert_blendshader = "0"
>
</power_fractal_shader_v3>
</terragen_clip>
A regular Perlin terrain should be nice and smooth-rolling, keep the octaves low, I'd use the same smallest scale as I would feature scale. Lead-in scale could also be the same but you might want it to be larger to spread out the features somewhat. I wouldn't use any other 'noise flavour' than Perlin, it should be smoothest.
Try a few 'random seed' clicks on this clip, should be good for such a terrain. You can also mess around with the warp and variation settings, above they're all the defaults from adding a new power fractal terrain in the 'terrain' tab's 'add terrain' button.