I am personally a Bosmer because the speed passive synergizes really well with the Bow passive and works in Stealth, unlike Orc which requires you to be sprinting.
This makes Bosmer best for a invis cloak playstyle, in my opinion. Imperial and Khajiit in second.
Orc is pretty good for a Dark Cloak brawler build as you get an extra bit of health and the sprint passive can be used more often.
However I think Nord will be even better as 4k resists is really strong, as well as chilled resistance.
Race don’t really matter especially in pvp imo because they all bring something good to the build. My main stamblade is a Breton partly role play because I Iike the race but the spell resistance is just amazing and my magic sustain so good I have amazing up time on shade and cloak it’s amazing in 1vx situations. I do however have an orc and wood elf stamblade to and I prefer orc because of the healing it brings 258 wd is strong and I know plenty of good stamblades who like khajit to.