5.5 naked eye, 12.75 with the scope, on a good night.
I wonder if could catch 10 mag galaxies if I can see 12.75mag stars...
If the galaxies are small and that brightness, then yes.
If the galaxies are large, probably not.
There are 2 magnitude figures, both of which have to be taken into account to determine visibility.
There is the Total Integrated Magnitude (the one often quoted) which is the brightness of the galaxy if the galaxy were compressed to about one square arc minute.
Then there is Surface Brightness, which is the brightness of the extended galaxy per square arc-minute (or arc-second in different figures).
A good example of how they can compare is M33, which has a TIM of 5.7, Wow, that's bright!
But, the average SB is 14.1, and wow, that's faint.
So you really need to know both figures to determine the visibility of the galaxy in your scope.
A small magnitude 10 galaxy might have a SB of 11, and that would be a bright, easy galaxy compared to M33.
Lastly, you also have to take into account the Brightness Gradient of the galaxy.
That's the steepness or shallowness of the increase in brightness from the edge to the center.
Taking our example, M33, it has a moderately steep BG and its core is much brighter than the edges, so you'll see at least the core in a small scope.
M31 in Andromeda has an even steeper BG and it's hard to imagine a sky so bright the core wasn't visible in a telescope.
NGC891 in Andromeda, on the other hand, has a very shallow BG and the center is only a trace brighter than the edges, making it hard to see for
a lot of amateurs even though it has a high TIM.
TIM and SB are listed for many galaxies in reference works, both printed and on-line.
BG is not, though knowing the brightness of the center square arc minute would be useful to know for the larger galaxies.
If two hypothetical galaxies of TIM 9.0 peaked at 4.0 and 10.0 respectively, you could pretty much know in advance which one would be easier to see in an urban/suburban setting.