the filters help a lot to increase the contrast of the photosphere features.
I have always mounted on the Herschel prism, after an ND3, a Baader Continuum filter, excellent for increasing the details of sunspots and facular areas.
My model is from many years ago, so I have to combine a UV / IR cut filter for maximum contrast.
In the new series it seems there is no longer a need for the uv / ir cut filter.
Before spending on the Continuum filter you can try a simple green filter, always after the Herschel prism and an ND3 filter, of course.
I use the ND 1.8 filter only for photographs.
Already with a green filter you will see a good improvement in the image, while the Continuum has an edge but costs enough.
On the 127mm refractor you can try the 1.25 "prism, but you will see that it will get very hot.
In fact, I switched to the 2 "model, just to avoid this problem.
For images, if you have the option, switch to a monochrome camera.
Compared to the SLR you will need a connected PC, but the results will be better, even with the less expensive camera models.
I started with analog video surveillance cameras ...