For the 200 × 245 cm wall, I’d make the centre waterfall about 70 cm wide, with the side waterfalls about 35–40 cm wide each.
The 86 cm depth can accommodate a proper collection basin while still leaving room for the pumps, plumbing access and a raised decorative front edge.
I would also make the centre waterfall lip around 205–215 cm high, with the side waterfall lips around 145–155 cm high.
This will give you the dramatic high centre + lower sides + two bubbling jets appearance you want.