As shown in the manual, to find the value for a given baud rate, use the equation (1000000/baud)-20. This doesn't work for serin2/serout2 @ 115200 bps.

With DEBUGIN it's simple.

DEFINE DEBUGIN_REG PORTC
DEFINE DEBUGIN_BIT 7
DEFINE DEBUGIN_MODE 0 '1 = Inverted, 0 = true
DEFINE DEBUG_BAUD 115200

Yes. There are ways to trick PBP into working at higher data rates with serin2 & serout2, but then everything else in your program is whacked timing wise since PBP adjusts timing for everything else based on the defined osc speed.