if you click on the enemy at the top center of the screen will be the enemy's information. A red number is higher than your level, iirc enemies lower than your level will be shown as a negative number.
My Romulan Liberated Borg character made it to Level 30 and beat the (old) Defense of New Romulus with the skill point bug.
When you select an NPC, you can see several bars ("rank pips") that dictate how powerful it is. One pip is easy, two is medium, three is hard, four is very hard. Most of the time, four pips means you can't defeat it on your own, so you'll need the help of either your Boffs or other players/NPCs.
For example, this one has two pips, meaning it's medium difficulty.