Do you tape kraft faced insulation?
Yes, you tape any insulation's lateral seams, especially any fluffy stuff...aluminum HVAC tape lasts the longest. The fluffy stuff really only works best in dead air space. Which also means the un-faced side (where you don't tape anything). If there's a good swap of air or you can feel a breeze when it's windy out, you'll want to seal that out.

1/4" Rigid Foam boards are good for this as they'll seal out most air movement, but still allow humidity to escape into the venting. I think they still have them, the accordion style works very well if you have a number of larger open areas within the truss structure. Otherwise, get the same size as your batts &amp; just put the foam on top.