In Rhino 8 curve drawing lag is a long-standing issue for me, I don’t know if it was reported yet.
The blinking Cursor Tooltip is a new thing because I wasn’t using it in the past.
In RH7 Tooltip decreases performance and aggressively blinks, in RH8 performance is already decreased, and blinking is making things worse.
The orange circle is from my software to show mouse clicks.
Rhino 8 - with Cursor Tooltip
Rhino 7 - with Cursor Tooltip
Rhino 8 - without Cursor Tooltip
Rhino 7 - without Cursor Tooltip