Replacing RichAuto A11 handle with PC control (LinuxCNC/Mach/UCCNC) on AC servo

Hi everyone,
I'm working on a KEGEMA-branded CNC router (1300x2500mm working area) that currently runs on a RichAuto DSP A11 handheld controller. I'd like to bypass the handle and control the machine directly from a PC (jog, home, run G-code, start/pause) — similar to what was done in this thread:
forum.linuxcnc.org/30-cnc-machines/35371...troller-richauto-a11
I've read that thread carefully and it's been very helpful, but my setup differs in one important way: my machine uses AC servo motors, not steppers.
Machine specs
Working size: 1300x2500x200mm
Spindle: 6kw HQD air-cooled
Spindle inverter/VFD: 7.5kw Fuling (brand: Folinn on the unit itself)
Axis motors: Leadshine 750W AC servo motors + matching Leadshine AC servo drivers (model marking "L7", 750W, one per axis: X, Y1, Y2, Z — Y1/Y2 appear to be a dual-motor gantry setup)
Reducer: Shimpo (Japan)
Control: RichAuto DSP A11 handheld controller
What I've already confirmed
Inside the control cabinet, the A11's interface board has clearly labeled screw terminals (not just a blind 50-pin harness like in the thread above):
INPUT SIGNAL row: X1 (XH/X-home), X2 (YH/Y-home), X3 (ZH/Z-home), X4 (TS/tool setter), X5-X8 spare, 24V/GND/SHIELD
OUTPUT row: Y5-Y8 + GND (relay outputs — dust collector, water pump, etc.)
Separate 4-pin terminal blocks per axis labeled X_AXIS, Y_AXIS, Z_AXIS, C_AXIS, each with 5V / PULSE / DIR / SHIELD
Each axis terminal block has its own cable running directly to its Leadshine servo driver's CN1 connector
Since these are screw terminals (not a sealed connector), my plan is to add a second wire in parallel at each terminal (tap-off) rather than disturb the existing A11 wiring, so the A11 handle stays functional as a fallback.
What I'm unsure about / looking for help on
Pulse/Dir signal type from Leadshine 750W AC servo drivers (L7 series) — are these standard 5V single-ended step/dir inputs, or differential (like the RS422 signals in the referenced thread)? Trying to confirm from the datasheet before wiring anything.
Recommended motion controller for a 4-axis (X, Y1, Y2 as dual Y, Z) AC servo setup — Mesa 7i96 vs 7i76e vs something else? Do I need differential drivers (like the AM26L31CN used in the referenced thread) between the A11 board and the controller card?
Dual Y-axis (gantry) handling — should Y1 and Y2 be wired as one LinuxCNC axis with a single driver output, or does anyone have experience keeping them as two synced axes?
Spindle speed control — my board also has S0-S3 speed-select terminals (7-speed selection, not analog 0-10V). Anyone dealt with converting this to continuous VFD speed control from LinuxCNC/Mach, or is it easier to just leave spindle speed control on the VFD's own panel?
Any gotchas specific to RichAuto A11 + AC servo (vs. stepper) retrofits that I should know before starting?
Happy to share more photos of the interface board and servo drivers if useful. Any pointers, schematics, or "here's what worked/didn't work for me" experiences would be hugely appreciated.
Thanks in advance!