Of course it is.
N64 was never a selling point for full PSP access on Vita; even if people DID use the PSPEmu for N64, DaedalusX64 isn't exactly a full-featured product worth the hassle.
Disable Digital to Analog in the controls subsection of the Quick Menu (Which lets you map the D-Pad to the analog sticks; when disabled, if the DualShock controller was supported in the game to begin with, the sticks act as just that. If not, the controller ceases to work.)
The touchscreen can be used: In the main menu -> Controls subsection, "Enable Touchscreen" should be on. From there, it defaults to the front touchscreen; enable "Prefer Rear Touch" to use the rear instead, as only one or the other can be used.
The four corners of the front/rear touchscreen/pad act (From top-left to bottom-right) L2, R2, L3, and R3. Map these controls as necessary for the cores.
I also recommend using "L3 + R3" for the Menu shortcut.