ATtiny V-USB with 115200bps? DIP only
Because software USB on AVR can only be 1.0 which is 1mbit max. If we subtract overheads on USB protocol and processing, even 384kbit looks awesome. If you need more - take specialized chip from FTDI for example.

SOIC soldering is not hard, and possible without fancy equipment.
If you want to prototype with SOIC you can solder tiny wires to leads.