Generally imaging filters are to enable the imaging to select a specific wavelength.
So they use say Ha, OIII and Hb.
Ha is simple, it is the one up in the red area.
OIII and Hb are less simple, they are fairly close to each other.
So the bit they pass is narrow, otherwise your image is both OIII and Hb.
Visual tends to be to enhance, not boost, a specific wavelenth or set of wavelengths. As such they can be wider, as much as to allow more light into the eye as anything. So you could find that a nebula filter passes both OIII and Hb to the eye. But what it does more relevantly is block the general atmospheric crud so that the OIII and Hb stand out a bit better.
Some "nebula" filters pass OIII, Hb and Ha, but block the stuff in the middle. The Ha is open to question - eyeball operation.
So for imaging select the wavelengths you want to capture and buy the relevant filter. They seem to come in 7nm, 5nm and 3nm widths. The narrower then the more expensive. Less is more in this case, sometimes a lot more.
Likely 2" are safer, they should not encroach in to the light path. And they can be fitted to a 2" diagonal and you can change eyepieces without having to swap filters (visual).
For visual it is common that the first filter is an OIII, or similar/suitable nebula filter. Just remember that the target need to be suitable. Galaxies and globular clusters tend not to benefit as they are "white".
If you can borrow a filter or two it is likely worth it. There is a fair bit of misunderstanding about filters.
There are filters that pass 3 wavelengths (fairly narrow bands), you will have to search, not sure of the application area.
So visual, a nice OIII filter. Imaging is whatever fits the filter wheel and the bandwidth passed and your processing.