No he is not typical LE.
Frank Castle is LE. Roose Bolton and Tywin Lannister are LE. Steel Brightblade is LE. Artemis Entreri is LE. Lord Soth is LE. For the latter three they have DnD stats that clearly show they're LE.
Darth Vader is nothing like any of the above. The three examples of LE have
clear codes of conduct they follow (never attacking an unarmed man, never attacking an unworthy foe, fighting with honor etc). Vader has nothing even close.
Lawful Evil PCs have a respect for family, honor and tradition, are disciplined and follow a code that (in their eyes) makes them more noble that the standard villain.
Vader has
none of that. The only 'code' he follows is the Sith code, which is summarized as basically 'Act CE, follow your base emotions, give in to hatred and anger, betray and kill your master'. His word means nothing, he was prepared to maim, turn over to the Emperor and even personally kill his own son (and wife) before finally redeeming himself to save Luke, he has no respect for traditions literally destroying the Jedi, Republic, Sith
and Empire in his lifetime, follows no law (other than the Emperors orders, and he betrays the Emperor when he can get away with it).
He betrays literally everyone he cares about, and kills or tries to kill them.
Lawful Evil:
Lawful evil
Vader did not play by the rules (as a Jedi or Sith). He broke promises willy nilly. He had no personal code of conduct as a Sith and would murder a person in cold blood as they slept, stab them in the back, cut down defenseless enemies, torture women, slaughter children, or coldly watch on as billions were killed by the Death Star.
You're conflating the fact that he is a CE servant of a LE Empire. He works for the Empire (sure). But its no different to how one can be CG servant of a LG empire, church or group.
He literally existed outside and above the law, followed no code at all, never kept his word, attempted to kill every single member of his family other than his mum, killed his best friend, attempted to kill both apprentices, killed both masters and the list just goes on and on and on.
There was literally noting Lawful about him other than the regime he worked for.
Darth Vader shows
restraint now?
In what possible way? Any direct attempt on Palpatine would see him dead, and when he finally did attempt it (after trying to convince literally everyone to help him in the act), it literally killed him in the process.