...The remastered with new effects and space scenes are cartoon-looking and seeing such shots jammed into a show that looks very 60s otherwise, is jarring...
The remastered new effects and space scenes are not
cartoon-looking, and while some episodes were done better than others, none of them look terrible.
Yes they do!
Vulkhan - definitely get the originals if you can. Failing that, I'd go with the Blue Ray idea, so you can have the original in addition to the awful, cartoony desecrations.