If you purchase two AT-STs, could you use two twin light blasters or two concussion grenades on one AT-ST instead of one of each?

"A unit cannot equip more than one copy of the same upgrade card." Page 22 of the Learn to Play.

Thank you, I missed that.

And let’s all be thankful you can’t.

Does the Mortar Launcher give out 2 suppression tokens if a hit or crit are rolled? Is the suppressive keyword in addition to tje normal suppression rules?

It adds two, one for the suppressive keyword and one for the ranged attack. Look under suppressive in the rule book.