На сеггере увидел упоминание о сабже. В SWD скорость в 10 раз выше. Кто нибудь работает с таким?

не в SWD. А в SWV . Это разные вещи. swv пока софтом не поддерживается.

Или хотя бы словесное описание различий в схемах электрических принципиальных от JLink v5.

9.6.1.4 Version 5.2
Identical to version 5.0 with the following exception:
Target Interface
nTRST is push-pull type
RESET is open drain
9.6.1.5 Version 5.3
Identical to version 5.2 with the following exception:
• 5V target supply current limited
5V target supply (pin 19) of Kick-Start versions of J-Link is current monitored
and limited. J-Link automatically switches off 5V supply in case of over-current to
protect both J-Link and host computer. Peak current (<= 10 ms) limit is 1A,
operating current limit is 300mA.
9.6.1.6 Version 5.4
Identical to version 5.3 with the following exception:
• JTAG interface is 5V tolerant.
9.6.1.7 Version 6.0
Identical to version 5.4 with the following exception:
• Outputs can be tristated (Effectively disabling the JTAG interface)
• J-Link supports SWV (Speed limited to 500 kHz)
9.6.1.8 Version 7.0
• Uses additional pin to the UART unit of the target hardware for SWV support
(Speed limited to 6 MHz).

Version 6.0
Identical to version 5.4 with the following exception:
• Outputs can be tristated (Effectively disabling the JTAG interface)
• J-Link supports SWV (Speed limited to 500 kHz)
Version 7.0
• Uses additional pin to the UART unit of the target hardware for SWV support
(Speed limited to 6 MHz).