Your right, sucker branches suck resources from the plant. Trimming is a road you need to cross atleast 2-3 weeks before you decide to flower the plant. There's allways options with everything. You can trim sucker branches, along with the first couple of branch nodes from the bottom. You can just trim the buds starting to grow on these branches pinching them off as the grow leaving the end of the branch flower set. You could trim nothing and do a 1/2 harvest harvesting the biggest buds leaving the bottom branches in flower a couple more weeks. It's a fine line to say what to leave and what to cut, cut to much and the plant suffers. Don't cut enough the plant wants to spread the energy to all branches taking away from all buds to support sucker branches.
look on life for tomatoe pruning, there's alot if good info you can apply to cannabis .