The drilled tanks are meant for a sump setup. If you don't use a sump, you can block off the holes with bulkheads & standpipes that are above the water line (or plugs if you have threaded bulkheads). You can then use the canister as per normal.
If you have an overflow box setup, you can utilize the drilled holes for your FX5 hookup. Without an overflow box, I would only hook up the canister if the both lines have standpipes so you are skimming water from the top of the tank & returning water to the top. <Reason is that if you have the lines at the bottom of the tank, and there is a leak with any of the hoses, you will drain your tank completely ....>
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.