I thought Tarkin looked okay. I mean he looked fake and like a video game model, but it was fine because that's what it was. Not as good as Michael Douglas in Ant-Man or RDJ in Civil War, but still a decent effort. It was about on par with the young Arnold from Terminator Genisys. You know it's weird and not real but you just go with it.
Leia was too creepy though. That didn't work. I'm still getting nightmares from that face.
That was ballsy of them to try and tackle ANH Leia. Like with action figures there is no more unforgiving likeness than a young lady. With Tarkin they had lots of nooks and crannies in his face to fall back on and sell the illusion that he was real. Like you said though, I'd put him on par with 1984 Arnie in Genisys. With Leia I didn't think she looked bad per se as far as realism is concerned but it just didn't quite match Carrie's likeness. Still a cool scene and I'm sure it'll look lightyears better at home then on a 15/70 IMAX screen.
When Tarkin first showed up I got nervous but the way they did his first scene with the poor lighting I thought, "okay, not bad, maybe that's all there is" and then when he kept coming back I got concerned that it was going to take me out of the movie. But that pay-off with him showing up on Scariff. Hell yeah, made it all worth it. So I'm more than fine with how he was handled.
Vader was off the charts though. I got a chuckle that his planet was the ONE planet that didn't get an identifying subtitle. Almost like Gareth was saying, "um, yeah, you can assume this is Mustafar if you want or you can just imagine it to be whatever generic lava planet he used to live on BEFORE the prequels were made." Well played Gareth.
I love the idea that he spends as much time as possible naked in a bacta tank, sans all mechanics. Especially juxtaposed with how ruthless he was in the suit.