There's obviously more to the AFP question than I'm comprehending as SH2 is protocol agnostic in that context?
FWIW I run both my Mac's wirelessly to my DS411J NAS via AFP and use Time Machine. Here's a log while I was testing with SH in router mode:
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Rgds - TW
20+yrs customer currently on Vivid 200/20Mbps service tier via SH3(VMDG505) hardware:v10 firm/software: v9.1.1912.304 and/or <cough> others,
provisioned from brig19 Arris E6k (BN3 7Nx node).