I use a Noblex 150F for which the slow speed module is not available but the shutter speeds go down to 1/15 as opposed to the 1/30 that is true for some other models. I use multiple exposures frequently and have never had a problem. Before I bought the Noblex I tried a Horseman G617, a Seitz Roundshot and a Widelux. The Horseman and like cameras are nice bu tthey are not panoramic in the true sense of the word. The Seitz drove me nuts and the Widelux just wasn't up to the same standards as the Noblex. The Noblex, BTW paid for itself on one job.
I don't use the filters so I can't address that issue either but the F model does have the zone focus feature and I wouldn't give it up. Actually, it is continuous zone focus with three detents. Yes, the lens is among the sharpest made and if you can accurately zone focus it gets even sharper. BTW, I don't know where the lenses are manufacured now but they were originally Docter Optics.
Every once in a while I will use the camera handheld at a higher shutter speed ... generally a bad idea ... keep it on the tripod. I have run literally hudnreds of rolls of film through this camera in the 5 years I have had it and it is a marvelous performer. PM me for any specific info you might be interested in.