I don't think they make them in a 1.95. The widest the Marathons seem to go is 1.75. These will work fine. The various tyres I use on my rims vary from 1.9 to 2.35. Marathons are just skinnier to reduce rolling resistance.
The width is just the measurement of the trye face. The bit that fits in the rim is all the same-ish. I think (and someone correct me if I'm wrong) that it's once you go below 1.5 the only real consideration you'll have is that the wider tubes may need changing.