I'd drop the Nebustar as it is mostly a visual filter and apparently blocks H alpha in emission nebula. It probably only passes H beta and OIII spectral lines greatly dimming stars to help certain emission nebula when seen visually. Most of these also emit H alpha making that filter a better choice for them as that emission line is usually stronger than the other two combined but poorly seen by the human eye. Both would severely dim star fields and galaxies over a luminance filter.

H alpha is can be used for luminance filter ONLY with emission nebula. Even then it requires extensive exposure time, I use at least 3 times more than I do luminance, 4 or 5 is better. You are only passing a very tiny part of the spectrum so are throwing away 99% of the light of broad spectrum objects like stars and galaxies but passing a significant portion of it for emission nebula. Note reflection nebula, often associated with emission nebula will be lost however.

It is very good for such nebula in light polluted skies. You don't say what your sky is like. It is also useful for some galaxies that are rich in H alpha like M82 but only to augment the luminence data not to replace it!

In my 5 filter wheel I use luminance, red, green, blue and H alpha. But I live under very dark skies.

If imaging from within Winnepeg's light polluted skies you may want to focus your attention on emission nebula and forget the LRGB filters replacing them with SII, H alpha and OIII filters. That's considered the best solution to heavily light polluted skies. But does limit you to emission nebula but that still leaves you a lot of targets.

Rick