When I started using 2.90 version, Pose mod started to lag (when choosing some bone). There are no lags in previous versions. I have: RAM 16 gb, 64-bit OS, AMD Athlon X4 840, Nvidia GeForce GTX 960
2 Answers
Have you tried unchecking File -> User Preferences -> Viewport -> Selection -> OpenGL Depth Picking? I had the same problem, but when I disabled this it seemed to be fixed.
Had this issue recently - In my case it was due to having multiple modifiers calculating after the armature in the modifier list. Try re-arranging them or simply applying them before you pose.
As a side note, I duplicate meshes I am about to apply modifiers on so that If I make a mistake down the line, I haven't 'destroyed' the original model. Hope this is helpful to someone.