Apu2c2 and mSATA SSD


I'm about to receive my apu2c2 to replace an old ASUS AC3200 which has some performance problems over 1G WAN links.
I plan to use a mSATA SSD to put OpenWRT on it. No issues to use the squashfs image ? Any smart way to use the remaining space on the mSATA SSD (64G) ? I can increase the partition before putting the SSD into the apu2c2, but what is the best partitioning layout/openwrt image to use for such combination ?