Go to the filter menu and blurs and Gaussian blur in Photoshop
There is only one, radius. You can apply very subtle haze by setting the radius value to a low setting or you can totally zap an image by pushing it to the limits though the higher the setting, the slower the response. Or go for an extreme with a high radius setting
Unless you are going to use brushes or manipulate the pixels of an image, you can always convert the current layer before any processing is applied and turn it into a smart object via the layer menu and smart objects and convert to smart object. You can then attach any effects applied to the current layer or image and the effect is then easy to remove as well as easy to edit and you can double click the entry and the panel will re-appear and you can edit it. You can also add multiple smart effects and then move them around and they can all have different settings or strength and can be blended with the lower entries. You can also add an image menu and adjustment into the mix.
You can apply the effect to the entire image which is fine but if you want to apply the effect to only a small part off the image then you can use selections to limit it. You can use a variety of selection tools but at the most basic of levels go to the rectangular marquee tool and then add over a part of the image and then apply the effect. There is a limit to this approach in that the selection is created before you apply the effect and them can't be changed later. That is the case if you use it as a normal layer.
If you convert the layer to a smart object then you can add your selection as normal and then add the effect but now you will see the selection as a mask and you can add to the mask as well as change the mask as well as clear it etc. Select the mask thumbnail for the smart effects for that layer and then go to the shape tool and set the color to white and add that as a pixel design to the thumbnail, that area will now be dulled in the same way as the earlier selection
You can also use clipping masks made out of vector shapes to control the range of the manipulation of the pixels. You can select a layer and if you want convert it into a smart object and then add some vector shapes, any shape design as long as it is a shape layer and then drag that shape layer to below the image layer and with the image layer selected go to the layer menu and select create clipping mask. You can also select the current layer and apply the effect and the effect will only appear based on the generated shapes and the rest of the layer will be transparent. If you wish to see the rest of the image, just duplicate the original image and have that below the clipping mask.
You can use it in RGB but if you display the channels panel found via the window menu, you can select the red channel and then apply the effect to that with one setting and then select the green channel and apply a different setting for that and so on with the blue channel. You can also create a new channel via the channels panel. You can select the current image and paste this into the alpha channel and you can then apply it as well as the neural or displace or twirl etc and that effect will modify the alpha channel. You can then go back to the standard RGB and then go to the select menu and use the load selection command and load that alpha channel with the result of the effect. You can then use that with gradients etc or [perhaps copy and paste that layer using the selection and then add a layer style such as bevel to the new channel and the bevels can be nearly unlimited with different contours and embossing etc.
It can be used with shapes such as pixel designs but also with layer option for the shapes. The vectors can be any size and they can be filled with gradients as well as patterns and can have effects added to them such as shadows and bevels but that works well with the effect as well, as long as you use it with the smart object or just rasterize the layer via the layer menu.
You can also apply it to type though as soon as you do this a panel will appear and ask whether you want to rasterize (turn it into a pixel layer) or turn it into a smart object, generally I go for the smart object as you can change things (within limits) later. Apply it with a setting of 40px etc and you will have a hazy set of characters to work with. Go to the layers panel and you will see the smart object and entries associated with it. Click on the thumbnail smart entry for the effect and then go to the gradient tool and select the black and white linear gradient and apply from top to bottom of the mask. You will now see the top of the type still all hazy. The area in the mask set to black has the type still super sharp.
You can flatten type into a layer and the effect can then be used slightly different, no smart objects involved. Type something (in white) on a black background layer and go to the layer menu and flatten. Apply it using a setting of 40px etc for the radius. Go to the edit menu and fade and set the blend to darken and you get an interesting inner shadow effect. Repeat that multiple times and you will still have sharp text but the text will now have a random pulsed look. Go to the image menu and adjustments and levels and move the input highlight to the left. The effect can be applied multiple times and combined with other effects and fades can be used to create all kinds of type manipulation.