drains

Is it a rule to glue The PVC to the sump bulkhead on the top side? is there any pros and cons? And what about the bottoms side

Currently in the middle of plumbing a 45 gal cube with a small overflow with two 1" drains. However my Proclear Aquatics Freedom 4-in-1 100 refugium only has one 1" input. Should or can I plumb them together so they both drain int to the 1 input? As pictured (Will that have any restrictions on...