Question 1:Any item that shares a recast type (For instance, the two items you mentioned share Recast Type: 2) with another item will render both items unusable when either is clicked, until the clicked timer has counted back down to zero - as you saw.
I learned this the hard way back when I had
webtools/items.php?id=6261 and
webtools/items.php?id=6393. Both items have Recast Type: 8. I used the ring (24 hr recast) and locked out my prized CoH orb for a whole day. That was a painful lesson =(
To be clear, if you have two items of the same Recast Type, with different recast timers, both will be locked out for the recast timer that you just clicked. If you clicked the short one, then both will be ready to be clicked again in a short time.
Question 2:Case 1 - two of the same item. Let's say it's
webtools/items.php?id=18397. Great clicky effect, but having two of that item will not give you two separate recast timers, unfortunately. Clicking one will lock out both, as per my answer in question 1.
Case 2 - two different items with the same effect. It all comes down to the Recast Type: #. If they're the same, they will share a timer. If they're different, then you may click both independently of one another.