I think it is important not to give up things that you do for the sake of Allah - Hijaab and/or niqaab, just for the sake of marriage. Because your intentions are to please Allah (swt) he will inshallah will reward you in many ways - one of which may include a spouse who accepts your niqaab.
But to answer your questions:
Most guys I know who are somewhat religious definitely want to marry a hijabi girl. However, the niqaab could be an issue if it is not common culturally to see women wearing the hijaab in the country of residence. However, the very religious brothers don't mind niqaab. P.S., most of these brothers are very well educated and they are religious as well.