For filters and polarizers I suggest high end. Lower quality filters can impair IQ.
46mm is a typical size for m4/3 so I advise to get B+W MRC. High end filters from other brands start at larger sizes. BHPhoto sometimes has B+W MRC linear polarizer in stock, I bought it there, works fine.
Linear is a bit less expensive than circular from the same product line, but they are harder to find. I believe linear PL have one layer less than circular so theoretically quality degradation should be less. With good CPL quality degradation is minimal, hardly noticeable, so the "linear vs circular" question may not be important. You won't be able to use linear on DSLR and most likely neither on Nikon 1 with PDAF.
I also got Marumi CPL in 46mm. Although it's not their top 99.5% transmittance line it works fine, no noticeable quality degradation. CPL and linear PL combined provide variable ND with 3-7 stops light loss without color cast. I also have 3 stop ND and combining 3 filters gives almost 10 stops light loss. But with 3 filters on kit lens vignetting shows on wider than 17mm focal length. 18mm and longer is OK. Dedicated 10 stop ND filter would have been preferable. But I needed one polarizer and ND8 filter anyway. And 2filters.com had Marumi CPL for cheap, 10 stop ND would be way more expensive.
Unfortunately I didn't have a chance to use this "10 stops ND" for real shots. But I made test shots and I could see that there was no noticeable quality degradation.
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